Light-sensing apparatus and light-sensing method thereof

ABSTRACT

A photo-detecting apparatus is provided. The photo-detecting apparatus includes: a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer including: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×1015 cm−3, wherein a distance between the first surface and a location of the channel region having the peak dopant concentration is less than a distance between the second surface and the location of the channel region having the peak dopant concentration, and wherein the distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation-in-part of and claims the priority to U.S. patent application Ser. No. 16/282,881, filed Feb. 22, 2019, which claims the benefit of U.S. Provisional Patent Application No. 62/634,741, filed Feb. 23, 2018, U.S. Provisional Patent Application No. 62/654,454, filed Apr. 8, 2018, U.S. Provisional Patent Application No. 62/660,252, filed Apr. 20, 2018, Provisional Patent Application No. 62/698,263, filed Jul. 15, 2018, U.S. Provisional Patent Application No. 62/682,254, filed Jun. 8, 2018, U.S. Provisional Patent Application No. 62/686,697, filed Jun. 19, 2018, U.S. Provisional Patent Application No. 62/695,060, filed Jul. 8, 2018, U.S. Provisional Patent Application No. 62/695,058, filed Jul. 8, 2018, U.S. Provisional Patent Application No. 62/752,285, filed Oct. 29, 2018, U.S. Provisional Patent Application No. 62/717,908, filed Aug. 13, 2018, U.S. Provisional Patent Application No. 62/755,581, filed Nov. 5, 2018, U.S. Provisional Patent Application No. 62/770,196, filed Nov. 21, 2018, and U.S. Provisional Patent Application No. 62/776,995, filed Dec. 7, 2018, which are each incorporated by reference herein in its entirety. This application also claims the benefit of U.S. Provisional Patent Application No. 62/862,687, filed Jun. 18, 2019, U.S. Provisional Patent Application No. 62/865,305, filed Jun. 24, 2019, U.S. Provisional Patent Application No. 63/006,696, filed Apr. 7, 2020, U.S. Provisional Patent Application No. 63/008,834, filed Apr. 13, 2020, U.S. Provisional Patent Application No. 63/012,249, filed Apr. 19, 2020, U.S. Provisional Patent Application No. 63/012,930, Apr. 21, 2020, which are each incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to a photo-detecting apparatus and a photo-detecting method.

2. Description of the Prior Art

Photodetectors may be used to detect optical signals and convert the optical signals to electrical signals that may be further processed by another circuitry. Photodetectors may be used in consumer electronics products, image sensors, data communications, time-of-flight (TOF) ranging or imaging sensors, medical devices, and many other suitable applications. However, when photodetectors are applied to these applications in a single or array configuration, the leakage current, dark current, electrical/optical cross-talk, and power consumption can degrade performance.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes a semiconductor substrate. A first germanium-based light absorption material is supported by the semiconductor substrate and configured to absorb a first optical signal having a first wavelength greater than 800 nm. A first metal line is electrically coupled to a first region of the first germanium-based light absorption material. A second metal line is electrically coupled to a second region of the first germanium-based light absorption material. The first region is un-doped or doped with a first type of dopants. The second region is doped with a second type of dopants. The first metal line is configured to control an amount of a first type of photo-generated carriers generated inside the first germanium-based light absorption material to be collected by the second region.

According to an embodiment of the present disclosure, a photo-detecting method is provided. The photo-detecting method includes transmitting an optical signal modulated by a first modulation signal, wherein the optical signal is modulated by the first modulation signal with one or multiple predetermined phase(s) for multiple time frames. The reflected optical signal is received by a photodetector. The reflected optical signal is demodulated by one or multiple demodulation signal(s), wherein the one or multiple demodulation signal(s) is/are the signal(s) with one or multiple predetermined phase(s) for multiple time frames. At least one voltage signal is output on a capacitor.

Among other advantages and benefits of the embodiments disclosed herein, the embodiments provide a photo-detecting apparatus capable of absorbing a least but not limited to a near-infrared (NIR) light or a short-wave infrared (SWIR) light efficiently. In some embodiments, a photo-detecting apparatus provides a high demodulation contrast, low leakage current, low dark current, low power consumption, low electrical/optical cross-talk and/or architecture for chip size miniaturization. In some embodiments, a photo-detecting apparatus is capable of processing the incident optical signal with multiple wavelengths, including different modulation schemes and/or time-division functions. Moreover, the photo-detecting apparatus can be used in time-of-flight (ToF) applications, which may operate at longer wavelengths compared to visible wavelengths (e.g., NIR and SWIR ranges) compared to visible wavelengths. A device/material implementer can design/fabricate a 100% germanium or an alloy (e.g., GeSi) with a predetermined percentage (e.g., more than 80% Ge) of germanium, either intrinsic or extrinsic, as a light absorption material to absorb the light at the aforementioned wavelengths.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes an absorption layer including a first surface; a passivation layer over the first surface of the absorption layer, wherein the passivation layer includes two first regions and a second region separating the two first regions, wherein each of the first regions includes a property, and the second region includes a property different from the property of each of the first regions.

In some embodiments, the property includes material or resistance.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes an absorption layer including a first surface; two second doped regions in the absorption layer; a passivation layer over the first surface of the absorption layer, wherein the passivation layer includes two intermediate regions each over respective second doped region, wherein each of the intermediate regions includes a peak dopant concentration lower than a peak dopant concentration of each of the two second doped regions.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes an absorption layer; two switches each including a control contact layer over the absorption layer; two buried counter-doped regions in the absorption layer and each at least partially under the respective switch.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes an absorption layer; two switches each including a control contact layer and a readout contact layers both above the absorption layer, wherein a distance between the two control contact layers is less than a width of the absorption layer, and a distance between the two readout contact layers is greater than the width of the absorption layer.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes a substrate and an absorption layer supported by the substrate; two switches electrically coupled to the absorption layer, and each switch including a first doped region and a second doped region, wherein the first doped regions are in the substrate, each of the second doped regions covers a part of an interface between the substrate and the absorption layer.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer; an absorbed region in the absorption layer; two switches each disposed at the same side of the absorbed region and electrically coupled to the absorption layer; a guiding region between two switches.

In some embodiments, each of the switches includes a control contact layer disposed at the same side of the absorbed region. The guiding region is between the portions of the absorption layer right under the two control contact layers.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer including: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×10¹⁵ cm⁻³, wherein a distance between the first surface and a location of the channel region having the peak dopant concentration is less than a distance between the second surface and the location of the channel region having the peak dopant concentration, and wherein the distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer including: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×10¹⁵ cm⁻³, wherein a distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm, and a distance between the second surface and the location of the channel region having the peak dopant concentration is not less than 30 nm.

In some embodiments, the absorption layer further includes a hinder region that is arranged between the channel region and the first surface.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer including a material having a first band gap; a carrier control layer on the absorption layer, wherein the carrier control layer includes a material having a second band gap greater than the first band gap and includes a thickness not less than 100 nm; and a readout contact layer on a first surface of the carrier control layer.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer including a material having a first band gap, wherein the absorption layer is capable of absorbing photons and generating photogenerated carriers; a carrier control layer on the absorption layer, wherein the carrier control layer includes a material having a second band gap greater than the first band gap, and the carrier control layer is capable of at least collecting the photogenerated carriers; and a readout contact layer on a first surface of the carrier control layer.

In some embodiments, the photo-detecting apparatus further includes a barrier region covering a part of the interface between the absorption layer and the carrier control layer.

In some embodiments, a dopant concentration of the barrier region at the interface between the absorption layer and the carrier control layer is not less than 1×10¹⁵ cm⁻³.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer; a first switch electrically coupled to the absorption layer; a second switch electrically coupled to the absorption layer; and a first modification contact layer configured to shape an electric field near the first switch; and a second modification contact layer configured to shape an electric field near the second switch.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer including a material having a first band gap; a carrier collection layer on the absorption layer, wherein the carrier control layer includes a material having a second band gap greater than the first band gap; two second doped regions in the carrier control layer, wherein each of the second doped regions has a depth, and the depth of each of the second doped regions is greater than a thickness of the carrier collection layer.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer; a preliminary collector in the absorption layer; and two switches electrically coupled to the absorption layer and disposed at two opposite sides of the preliminary collector.

In some embodiments, each of the switches includes a first doped region of a first conductivity type, wherein the preliminary collector is of a conductivity type the same as a first conductivity type of the first doped region.

In some embodiments, each of the switches further includes a second doped region. The preliminary collector overlaps with at least a portion of each of the second doped regions.

In some embodiments, the absorption layer further includes a hinder region connected to the preliminary collector.

In some embodiment, the hinder region is of a conductivity type different from the conductivity type of the preliminary collector.

In some embodiments, the photo-detecting apparatus further includes two counter-doped regions overlapping with at least a portion of the respective first doped region.

According to an embodiment of the present disclosure, a photo-detecting apparatus is provided. The photo-detecting apparatus includes: an absorption layer; and two switches electrically coupled to the absorption layer, wherein each of the two switches includes a first doped region; and a first buffer region and a second buffer region between the two first doped regions.

According to an embodiment of the present disclosure, an imaging system is provided. The imaging system includes one or more cameras; and a photo-detecting apparatus. In some embodiments, The photo-detecting apparatus includes a pixel-array for time-of-flight information, each pixel of the pixel-array includes a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer including: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×10¹⁵ cm⁻³, wherein a distance between the first surface and a location of the channel region having the peak dopant concentration is less than a distance between the second surface and the location of the channel region having the peak dopant concentration, and wherein the distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this application will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIGS. 1A-1J illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 2A-2H illustrate cross-sectional views of a photo-detecting apparatus with body depletion mode, according to some embodiments.

FIGS. 3A-3B illustrate cross-sectional views of a photo-detecting apparatus with gated body depletion mode, according to some embodiments.

FIGS. 4A-4H illustrate cross-sectional views of a photo-detecting apparatus with a lower leakage current and a lower dark current, according to some embodiments.

FIGS. 5A-5H illustrate a cross-sectional view of a photo-detecting apparatus with passivation layer, according to some embodiments.

FIGS. 6A-6C illustrate cross-sectional views of a photo-detecting apparatus with boosted charge transfer speed, according to some embodiments.

FIGS. 6D-6V illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 7A-7B illustrate cross-sectional views of a photo-detecting apparatus with surface depletion mode, according to some embodiments.

FIGS. 7C-7D illustrate planar views of a photo-detecting apparatus with surface depletion mode, according to some embodiments.

FIG. 8A illustrates a cross-sectional view of a photo-detecting apparatus with surface ion implantation, according to some embodiments.

FIG. 8B illustrates a planar view of a photo-detecting apparatus with surface ion implantation, according to some embodiments.

FIG. 9A illustrates a cross-sectional view of a photo-detecting apparatus with pixel to pixel isolation, according to some embodiments.

FIG. 9B illustrates a planar view of a photo-detecting apparatus with pixel to pixel isolation, according to some embodiments.

FIGS. 9C-9E illustrate cross-sectional views of a photo-detecting apparatus with pixel to pixel isolation, according to some embodiments.

FIGS. 10A-10D illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 11A-11E illustrate planar views of a photo-detecting apparatus with chip size miniaturization, according to some embodiments.

FIGS. 12A-12B illustrate planar views of array configurations of a photo-detecting apparatus, according to some embodiments.

FIG. 13A-13E illustrate blocks and timing diagrams of a photo-detecting apparatus using modulation schemes with phase changes, according to some embodiments.

FIG. 14 illustrates a process for using the photo-detecting apparatus using modulation schemes with phase changes, according to some embodiments.

FIGS. 15A-15B illustrate a top view of a photo-detecting apparatus, according to some embodiments.

FIGS. 15C-15D illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIG. 15E illustrates a top view of a photo-detecting apparatus, according to some embodiments.

FIG. 15F illustrates cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIG. 15G illustrates a top view of a photo-detecting apparatus, according to some embodiments.

FIG. 15H illustrates cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIG. 15I illustrates a top view of a photo-detecting apparatus, according to some embodiments.

FIG. 15J illustrates cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIG. 15K illustrates a top view of a photo-detecting apparatus, according to some embodiments.

FIG. 15L illustrates cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 16A-16M illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 17A-17I illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 18A-18U illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 19A-19D illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

FIGS. 20A-20M illustrate cross-sectional views of a photo-detecting apparatus, according to some embodiments.

DETAILED DESCRIPTION

As used herein, the terms such as “first”, “second”, “third”, “fourth” and “fifth” describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another. The terms such as “first”, “second”, “third”, “fourth” and “fifth” when used herein do not imply a sequence or order unless clearly indicated by the context. The terms “photo-detecting”, “photo-sensing”, “light-detecting”, “light-sensing” and any other similar terms can be used interchangeably.

Spatial descriptions, such as “above”, “top”, and “bottom” and so forth, are indicated with respect to the orientation shown in the figures unless otherwise specified. It should be understood that the spatial descriptions used herein are for purposes of illustration only, and that practical implementations of the structures described herein can be spatially arranged in any orientation or manner, provided that the merits of embodiments of this disclosure are not deviated by such arrangement.

FIG. 1A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 a includes a germanium-based light absorption material 102 supported by the semiconductor substrate 104. In one implementation, the semiconductor substrate 104 is made by silicon or silicon-germanium or germanium or III-V compounds. The germanium-based light absorption material 102 herein refers to intrinsic germanium (100% germanium) or an alloy of elements including germanium, e.g., silicon-germanium alloy, ranging from 1% to 99% Ge concentration. In some implementations, the germanium-based light absorption material 102 may be grown using a blanket epitaxy, a selective epitaxy, or other applicable techniques. The germanium-based light absorption material 102 is embedded in the semiconductor substrate 104 in FIG. 1A, and in alternative embodiments the germanium-based light absorption material 102 may be partially embedded in or may be standing on the semiconductor substrate 104.

The photo-detecting apparatus 100 a includes a control metal line 106 a and a readout metal line 108 a. The control metal line 106 a and the readout metal line 108 a are both electrically coupled to the surface 102 s of the germanium-based light absorption material 102. In this embodiment, the control metal line 106 a is electrically coupled to an un-doped region 105 a on the surface 102 s, where the un-doped region 105 a has no dopants. The readout metal line 108 a is electrically coupled to a doped region 101 a on the surface 102 s, where the doped region 101 a has dopants.

It is noted that the germanium-based light absorption material 102 can be formed as intrinsic or extrinsic (e.g., lightly P-type or lightly N-type). Due to the defect characteristics of the germanium material, even if there is no additional doping process introduced, the germanium-based light absorption material 102 may still be lightly P-type. Thus, the un-doped region 105 a may also be lightly P-type. The doped region 101 a may be doped with P-type dopants or N-type dopants, depending on the type of photo-carries (i.e. holes or electrons) to be collected. In some implementations, the doped region 101 a could be doped by thermal-diffusion, ion-implantation, or any other doping process.

The control metal line 106 a is controlled by a control signal cs1 for controlling the moving direction of the electrons or holes generated by the absorbed photons. Assume that the doped region 101 a is N-type and the control signal cs1 is at logic 1. An electric field is generated from the control metal line 106 a to the germanium-based light absorption material 102. The electrons will move toward the control metal line 106 a and be collected by the doped region 101 a. On the contrary, if the doped region 101 a is P-type, the holes will be collected instead. Alternatively, assume that the doped region 101 a is N-type when the control signal cs1 is at logic 0, a different electric field is generated from the control metal line 106 a to the germanium-based light absorption material 102. The electrons will not move toward the control metal line 106 a and so cannot be collected by the doped region 101 a. On the contrary, if the doped region 101 a is P-type, the holes will not be collected instead.

Using the structure illustrated in FIG. 1A, the optical signal IL reflected by a target object (not shown in FIG. 1A) and incoming through the optical window WD can be absorbed by the germanium-based light absorption material 102, and generate electron-hole pairs such that the electrons or the holes (depending on whether the doped region 101 a is N-type and P-type) are moving toward and being stored in the capacitor 110 a according to the assertion of control signal cs1. The absorbed region AR is a virtual area receiving the optical signal IL incoming through the optical window WD. Due to a distance existing between the photo-detecting apparatus 100 a and the target object (not shown in FIG. 1A), the optical signal IL has a phase delay with respect to the transmitted light transmitted by a transmitter (not shown in FIG. 1A). When the transmitted light is modulated by a modulation signal and the electron-hole pairs are demodulated through the control metal line 106 a by a demodulation signal, the electrons or the holes stored in the capacitor 110 a will be varied according to the distance. Therefore, the photo-detecting apparatus 100 a can obtain the distance information based on the voltage v1 on the capacitor 110 a.

The embodiments of FIG. 1A are a one-tap structure because they only use one control metal line 106 a and one readout metal line 108 a to obtain the distance information. The disclosed embodiments may also use two or more control lines or readout lines, and varieties of implantations to obtain the distance information, which will be described in detail hereinafter.

FIG. 1B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. Compared to the embodiment of FIG. 1A, the photo-detecting apparatus 100 b in FIG. 1B uses two control metal lines 106 a, 106 b to control the movement of the electrons or holes generated by the absorbed photons in the germanium-based light absorption material 102. Such a structure is referred as a two-tap structure. The photo-detecting apparatus 100 b includes control metal lines 106 a, 106 b and readout metal lines 108 a, 108 b. The control metal lines 106 a, 106 b and the readout metal lines 108 a, 108 b are electrically coupled to the surface 102 s of the germanium-based light absorption material 102. In this embodiment, the control metal lines 106 a, 106 b are respectively electrically coupled to the un-doped regions 105 a, 105 b on the surface 102 s, where the un-doped regions 105 a, 105 c are the areas without dopants; and the readout metal line 108 a, 108 b are respectively electrically coupled to doped regions 101 a, 101 b on the surface 102 s, where the doped regions 101 a, 101 b are the areas with dopant. The doped regions 101 a, 101 b may be doped with P-type dopants or N-type dopants.

The control metal lines 106 a, 106 b are respectively controlled by the control signals cs1, cs2 for controlling the moving direction of the electrons or holes generated by the absorbed photons. In some implementations, the control signals cs1 and cs2 are differential voltage signals. In some implementations, one of the control signals cs1 and cs2 is a constant voltage signal (e.g., 0.5 v) and the other control signal is a time-varying voltage signal (e.g., sinusoid signal, clock signal or pulse signal operated between 0V and 1V).

Assume that the doped regions 101 a, 101 b are N-type and the control signals cs1, cs2 are clock signals with 180-degree phase different to each other. When the control signal cs1 is at logic 1 and the control signal cs2 is at logic 0, the photo-detecting apparatus 100 b generates an electric field from the control metal line 106 a to the germanium-based light absorption material 102, and the electrons will move toward the control metal line 106 a and then be collected by the doped regions 101 a. Similarly, when the control signal cs1 is at logic 0 and the control signal cs2 is at logic 1, the photo-detecting apparatus 100 b generates an electric field from the control metal line 106 b to the germanium-based light absorption material 102, and the electrons will move toward the control metal line 106 b and then be collected by the doped region 101 b. On the contrary, if the doped regions 101 a and 101 b are P-type, the holes will be collected instead.

In accordance with this two-tap structure, the optical signal IL reflected from a target object (not shown in FIG. 1B) can be absorbed by the germanium-based light absorption material 102 and generates electron-hole pairs such that the electrons or the holes (depending on the doped region 101 a is N-type and P-type) move towards and are stored in the capacitor 110 a or capacitor 110 b, according to the assertions of control signal cs1 and control signal cs2. Due to a distance existing between the photo-detecting apparatus 100 b and the target object (not shown in FIG. 1B), the optical signal IL has a phase delay with respect to the transmitted light transmitted by a transmitter (not shown in FIG. 1B). When the transmitted light is modulated by a modulation signal and the electron-hole pairs are demodulated through the control metal lines 106 a and 106 b by the demodulation signals, the electrons or the holes stored in the capacitor 110 a and capacitor 110 b will be varied according to the distance. Therefore, the photo-detecting apparatus 100 b can obtain the distance information based on the voltage v1 on the capacitor 110 a and the voltage v2 on the capacitor 110 b. According to one embodiment, the distance information can be derived based on calculations with voltage v1 and voltage v2 as input variables. For one example, in a pulse time-of-flight configuration, voltage ratios related to voltage v1 and voltage v2 are used as input variables. In another example, in a continues-wave time-of-flight configuration, in-phase and quadrature voltages related voltage v1 and voltage v2 are used as input variables.

The control metal line 106 a in FIG. 1A and control metal lines 106 a, 106 b in FIG. 1B are electrically coupled to the un-doped regions of the germanium-based light absorption material 102. In other embodiments, as described below, certain structures and the control metal lines 106 a, 106 b are electrically coupled to doped regions.

FIG. 1C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. Similar to FIG. 1A, the photo-detecting apparatus 100 c includes a control metal line 106 a and a readout metal line 108 a. The control metal line 106 a and the readout metal line 108 a are both electrically coupled to the surface 102 s of the germanium-based light absorption material 102. In this embodiment, the control metal line 106 a is electrically coupled to a doped region 103 a on the surface 102 s, where the doped region 103 a is an area with dopants; and the readout metal line 108 is electrically coupled to a doped region 101 a on the surface 102 s, where the doped region 101 a is also an area with dopants. In this embodiment, the region 101 a and region 103 a are doped with dopants of different types. For example, if the doped region 101 a is doped with N-type dopants, the region 103 a will be doped with P-type dopants, and vice versa.

The operation of photo-detecting apparatus 100 c is similar to the embodiment of FIG. 1A. The control metal line 106 a is used to control the moving direction of the electrons or holes generated by the absorbed photons according to the control signal cs1 to make the electrons or holes being collected by doped region 110 a. By controlling the control signal cs1 and reading the voltage v1 on the capacitor 110 a, the photo-detecting apparatus 100 c can obtain a distance information between the photo-detecting apparatus 100 c and the target object (not shown in FIG. 1C).

FIG. 1D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 b includes control metal lines 106 a, 106 b and readout metal lines 108 a, 108 b. The control metal lines 106 a, 106 b and the readout metal lines 108 a, 108 b are electrically coupled to the surface 102 s of the germanium-based light absorption material 102. In this embodiment, the control metal lines 106 a, 106 b are respectively electrically coupled to the doped regions 103 a, 103 b on the surface 102 s, where the doped regions 103 a, 103 b are areas with dopants. The readout metal line 108 a, 108 b are respectively electrically coupled to the doped regions 101 a, 101 b on the surface 102 s, where the doped regions 101 a, 101 b are also areas with dopants. The regions 101 a, 101 b, 103 a, 103 b may be doped with P-type dopants or N-type dopants. In this embodiment, the doped regions 101 a, 101 b are doped with a dopant of the same type; and the doped regions 103 a, 103 b are doped with a dopant of the same type. However, the type of doped regions 101 a, 101 b is different from the type of the doped regions 103 a, 103 b. For example, if the doped regions 101 a, 101 b are doped as N-type, the doped regions 103 a, 103 b will be doped as P-type, and vice versa.

The operation of photo-detecting apparatus 100 d is similar to the embodiment of FIG. 1B. The control metal lines 106 a, 106 b are used to control the moving direction of the electrons or holes generated by the absorbed photons according to the control signals cs1, cs2 to make the electrons or holes being stored in capacitor 110 a or capacitor 110 b. By controlling the control signals cs1, cs2 and reading the voltages v1, v2 on the capacitor 110 a, 110 b, the photo-detecting apparatus 100 d can obtain a distance information between the photo-detecting apparatus 100 d and the target object (not shown in FIG. 1D).

FIG. 1E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The operation of the apparatus is similar to FIG. 1D, in which the apparatus is able to obtain to the distance information between the photo-detecting apparatus 100 d and the target object (not shown in FIG. 1E) by the way of generating the control signals cs1, cs2 and reading the voltages v1, v2 on the capacitor 110 a, 110 b. The difference from FIG. 1D is that the readout metal lines 108 a, 108 b and doped regions 101 a, 101 b are arranged at the surface 102 ss opposite to the surface 102 s. Because the control metal lines 106 a, 106 b and readout metal lines 108 a, 108 b are arranged in a vertical direction, the horizontal area of the photo-detecting apparatus 100 e can be reduced accordingly.

FIG. 1F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. Compared to FIG. 1E, the embodiment in FIG. 1F also arranges the doped regions 101 a, 101 b at the surface 102 ss opposite to the surface 102 s, but the readout metal lines 108 a, 108 b are extending toward the surface 102 s, rather than the semiconductor substrate 104. Such arrangements may simplify the fabrication process.

In some implementations, as the embodiments illustrated in FIG. 1A to FIG. 1F and the embodiments hereinafter, the control metal lines 106 a, 106 b and the surface 102 s can be made as a metal-semiconductor junction (MS junction) with Schottky barrier, or a metal-insulator-semiconductor capacitor (MIS capacitor) by introducing oxide or high-K dielectric materials as the insulator in-between the metal and the semiconductor.

As the embodiments illustrated in FIG. 1A to FIG. 1F and the embodiments hereinafter, the germanium-based light absorption material 102 is made as rectangular from its cross-sectional view, however, in some implementations, the germanium-based light absorption material 102 can be made as inverted trapezoid or other patterns from its cross-sectional view.

The photo-detecting apparatuses illustrated in the present disclosure can be used in time-of-flight (ToF) applications, which may operate at longer wavelengths (e.g., NIR or SWIR range) compared to visible wavelengths. The wavelength could be more than 800 nm, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, or 1550 nm. On the other hand, the device/material implementer can design/fabricate a 100% germanium or an alloy (e.g., GeSi) with a predetermined percentage (e.g., more than 80% Ge) of germanium, either intrinsic or extrinsic, as a light absorption material to absorb the light at the aforementioned wavelengths.

Although the embodiments herein illustrate that the photo-detecting apparatus absorbs the optical signal IL from a back side, however, in some implementations, the photo-detecting apparatus can be designed to absorb the optical signal IL from a front side, e.g., by creating an optical window WD between the two control metal lines 106 a, 106 b.

The embodiments illustrated in FIG. 1A to FIG. 1F include a single photodetector, which can serve as a unit and be applied to each pixel of a pixel array. The following descriptions are alternative embodiments based on either one-tap or two-tap structures disclosed in FIG. 1A to FIG. 1F. In the following descriptions, one or two embodiments from FIG. 1A to FIG. 1F may be selected as a representative embodiment. The person skilled in the art can change, modify or combine the structures disclosed herein, such as replace two-tap structure with one-tap structure.

FIG. 1G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 g includes a substrate 104′. The photo-detecting apparatus further includes a pixel (not labeled) including an absorption layer 102′ supported by the substrate 104′. The pixel includes an absorbed region AR in the absorption layer 102′ and defined by an optical window WD. The absorbed region AR is a virtual area receiving the optical signal IL incoming through the optical window WD. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 102′. The first switch includes a control contact layer 106 a′ and a readout contact layer 108 a′. The second switch includes a control contact layer 106 b′ and a readout contact layer 108 b′. In some embodiments, the readout contact layers 108 a′, 108 b′ are formed over a first surface 104 s of the substrate 104′. In some embodiments, a width w3 of the absorbed region AR is less than a distance d₄ between the readout contact layers 108 a′, 108 b′. In some embodiments, the readout contact layers 108 a′, 108 b′ are disposed at two opposite sides of the absorbed region AR. In some embodiments, a distance d₃ between the control contact layers 106 a′, 106 b′ is less than a width w₃ of the absorption layer 102′. In some embodiments, the first surface 102 s′ of the absorption layer 102′ is substantially flush with the first surface 104 s of the substrate 104′.

The photo-detecting apparatus 100 g includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the control contact layers 106 a′, 106 b′ are formed over both of the first surface 104 s of the substrate 104′ and the first surface 102 s′ of the absorption layer 102′. In other words, a part of the control contact layers 106 a′, 106 b′ is formed over the first surface 104 s of the substrate 104′ and the other part of the control contact layers 106 a′, 106 b′ is formed over the first surface 102 s′ of the absorption layer 102′. In some embodiments, the control contact layers 106 a′, 106 b′ cover a part of the interface between the substrate 104′ and the absorption layer 102′ along a vertical direction D1. The vertical direction D1 is substantially perpendicular to the first surface 102 s′ of the absorption layer 102′.

In some embodiments, un-doped regions 105 a, 105 b are right under the control contact layers 106 a′, 106 b′. That is, the portions of the absorption layer 102′ and the substrate 104′ right under the control contact layers 106 a′, 106 b′ may be intrinsic or include a dopant, each of the portions has a dopant profile with a peak dopant concentration below approximately 1×10¹⁵ cm⁻³. The term “intrinsic” means that the portions of the absorption layer 102′ and the substrate 104′ right under the control contact layers 106 a′, 106 b′ are without intentionally adding dopants. In some embodiments, the control contact layers 106 a′, 106 b′ on the absorption layer 102′ and the substrate 104′ may lead to formation of a Schottky contact, an Ohmic contact, or a combination thereof having an intermediate characteristic between the two, depending on various factors including the material of the absorption layer 102′, the material of the control contact layers 106 a′, 106 b′, the material of the substrate 104′, and the impurity or defect level of the absorption layer 102′ as well as the substrate 104′.

The pixel further includes two control signals cs1, cs2 controlling the control contact layers 106 a′, 106 b′ for controlling the moving direction of the electrons or holes generated by the absorbed photons in the absorption layer 102′. For example, when voltages are used, if the control signal cs1 is biased against the control signal cs2, an electric field is created between the two portions right under the control contact layers 106 a′, 106 b′, and free charges drift towards one of the two portions right under the readout contact layers 108 b′ 108 a′ depending on the direction of the electric field.

In some embodiments, the pixel includes two capacitors 110 a, 110 b. The readout contact layers 108 a′ is electrically coupled to the capacitor 110 a, and the readout contact layers 108 b′ is electrically coupled to the capacitor 110 b. The capacitors 110 a, 110 b are for storing the carriers generated in the absorption layer 102′ based on the control of the two control signals cs1, cs2. For example, due to a distance existing between the photo-detecting apparatus 100 g and a target object (not shown), the optical signal IL has a phase delay with respect to a transmitted light transmitted by a transmitter (not shown). When the transmitted light is modulated by a modulation signal and the electron-hole pairs are demodulated through the control contact layers 106 a′ and 106 b′ by a demodulation signal, the electrons or the holes stored in the capacitor 110 a, 110 b will be varied according to the distance. Therefore, the photo-detecting apparatus 100 g can obtain the distance information based on the voltage v1 on the capacitor 110 a and the voltage v2 on the capacitor 110 b.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit may include the capacitor 110 a. The second readout circuit may include the capacitor 110 b. The first readout circuit is electrically coupled to the readout contact layer 108 a′. The second readout circuit is electrically coupled to the readout contact layer 108 b′.

In some embodiments, the first switch includes a first doped region 101 a′ under the readout contact layers 108 a′. The second switch includes a first doped region 101 b′ under the readout contact layers 108 b′.

In some embodiments, the first doped regions 101 a′, 101 b′ are of a first conductivity type. In some embodiments, the first doped regions 101 a′, 101 b′ include a first dopant and a dopant profile. The peak dopant concentrations of the first doped regions 101 a′, 101 b′ depend on the material of the readout contact layers 108 a′, 108 b′ and the material of the substrate 104′, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 101 a′, 101 b′ are for collecting the carriers generated from the absorption layer 102′, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2.

FIG. 1H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 h in FIG. 1H is similar to the photo-detecting apparatus 100 g in FIG. 1G, where the difference is described below. In some embodiments, the first switch further includes a second doped region 103 a′ under the control contact layers 106 a′. The second switch further includes a second doped region 103 b′ under the control contact layers 106 b′. The second doped regions 103 a′, 103 b′ are formed in both the absorption layer 102′ and the substrate 104′. In some embodiments, each of the second doped regions 103 a′, 103 b′ covers a part of the interface between the substrate 104′ and the absorption layer 102′. The interface is substantially perpendicular to the first surface 102 s′. In some embodiments, the second doped regions 103 a′, 103 b′ are of a second conductivity type different from the first conductivity type of the first doped regions 101 a′,101 b′. In some embodiments, the second doped regions 103 a′, 103 b′ include a second dopant and a dopant profile. The peak dopant concentrations of the second doped regions 103 a′, 103 b′ depend on the material of the control contact layers 106 b′, 106 a′ and the material of the absorption layer 102′ and the material of the substrate 104′, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, a concentration at the interface between the substrate 104′ and the absorption layer 102′ and covered by the second doped regions 103 a′, 103 b′ is between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped regions 103 a′, 103 b′ forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 106 b′, 106 a′. The second doped regions 103 a′, 103 b′ are for demodulating the carriers generated from the absorption layer 102′ based on the control of the control signals cs1, cs2. By forming the second doped regions 103 a′, 103 b′ covering the interface between the substrate 104′ and the absorption layer 102′, the photo-detecting apparatus 100 h can with a satisfied dark current and demodulation contrast at the same time. In some embodiments, the control contact layers 106 b′, 106 a′ can be entirely formed over the absorption layer 102′ or be entirely formed over the substrate 104′.

FIG. 1I illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 i in FIG. 1I is similar to the photo-detecting apparatus 100 g in FIG. 1G, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 133 a between the absorption layer 102′ and the control contact layer 106 a′. The second switch may further include a second dielectric layer 133 b between the absorption layer 102′ and the control contact layer 106 b′. The first dielectric layer 133 a prevents direct current conduction from the control contact layer 106 a′ to the absorption layer 102′ and to the substrate 104′, but allows an electric field to be established within the absorption layer 102′ in response to an application of a voltage to the control contact layer 106 a′. The second dielectric layer 133 b prevents direct current conduction from the control contact layer 106 b′ to the absorption layer 102′ and to the substrate 104′ but allows an electric field to be established within the absorption layer 102′ in response to an application of a voltage to the control contact layer 106 b′. The established electric field may attract or repel charge carriers within the absorption layer 102′.

FIG. 1J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 100 j in FIG. 1J is similar to the photo-detecting apparatus 100 i in FIG. 1I, where the difference is described below. In some embodiments, the first switch further includes a second doped region 103 a′ under the first dielectric layer 133 a. The second switch further includes a second doped region 103 b′ under the second dielectric layer 133 b. The second doped regions 103 a′, 103 b′ are similar to the second doped regions 103 a′, 103 b′ described in FIG. 1H. In some embodiments, the control contact layers 106 b′, 106 a′, the first dielectric layer 133 a and the second dielectric layer 133 b can be entirely formed over the absorption layer 102′ or be entirely formed over the substrate 104′.

FIG. 2A illustrates a cross-sectional view of a photo-detecting apparatus with body depletion mode, according to some embodiments. The photo-detecting apparatus 200 a includes control metal lines 206 a, 206 b and readout metal lines 208 a, 208 b. The control metal lines 206 a, 206 b and the readout metal lines 208 a, 208 b are electrically coupled to the surface 202 s of the germanium-based light absorption material 202. The control metal lines 206 a, 206 b are respectively electrically coupled to the P-type regions 203 a, 203 b on the surface 202 s, and the readout metal line 208 a, 208 b are respectively electrically coupled to the N-type regions 201 a, 201 b on the surface 202 s. In some embodiments, the depth d1 of the P-type regions 203 a, 203 b extending from the surface 202 s is deeper than the depth d2 of the N-type regions 201 a, 201 b, and the germanium-based light absorption material 202 is lightly N-type. With deeper P-type regions 203 a, 203 b, larger depletion regions are created between the deeper P-type regions 203 a, 203 b and the N-type germanium-based light absorption material 202, which may allow electrons moving toward the N-type regions 201 a, 201 b when two different voltages are applied to the control metal lines 206 a, 206 b and therefore increases the quantum efficiency and the demodulation contrast. In other aspects, the width w1 of P-type regions 203 a, 203 b, the width w2 of N-type regions 201 a, 201 b, the doping concentration of P-type regions 203 a, 203 b, and/or the doping concentration of N-type regions 201 a, 201 b are also the parameters to adjust the area of the depletion regions.

In some embodiments, to fully deplete the body of the N-type germanium-based light absorption material 202, one can design through the N-type regions 201 a, 201 b and/or P-type regions 203 a, 203 b, either through its depths, widths or doping concentrations. Also, the thickness of the germanium-based light absorption material 202 should be designed accordingly.

FIG. 2B illustrates a cross-sectional view of a photo-detecting apparatus with body depletion mode, according to some embodiments. The photo-detecting apparatus 200 b can be designed with shallower P-type regions 203 a, 203 b. In other words, the depth d1 of the P-type regions 203 a, 203 b extending from the surface 202 s is shallower than the depth d2 of the N-type regions 201 a, 201 b. Applying shallower P-type regions 203 a, 203 b may reduce the leakage between the P-type region 203 a and P-type region 203 b.

FIG. 2C illustrates a cross-sectional view of a photo-detecting apparatus with body depletion mode, according to some embodiments. The structure of photo-detecting apparatus 200 c is similar to the photo-detecting apparatus 200 a, 200 b. The photo-detecting apparatus 200 c applies a bias voltage vb1 on the semiconductor substrate 204. This bias voltage vb1 is applied for creating a reverse bias across the junctions between the N-type germanium-based light absorption material 202 and the P-type regions 203 a, 203 b. As a result, the depletion region underneath the P-type regions 203 a, 203 b can be enlarged or even fully depleted. Due to the larger depletion regions generated underneath the P-type regions 203 a, 203 b, it may make allow electrons moving toward the N-type regions 201 a, 201 b when two different voltages are applied to the control metal lines 206 a, 206 b and thus increases the quantum efficiency and the demodulation contrast.

FIG. 2D illustrates a cross-sectional view of a photo-detecting apparatus with body depletion mode, according to some embodiments. Similar to the structure of photo-detecting apparatuses 200 a, 200 b, this embodiment applies a bias voltage vb2 on the germanium-based light absorption material 202 to control the depletion regions inside the germanium-based light absorption material 202. Specifically, the bias voltage vb2 is a reverse bias to the P-type regions 203 a, 203 b and the N-type germanium-based light absorption material 202, and so be able to enlarge the depletion regions surrounding the P-type regions 203 a, 203 b or even being fully depleted.

In order to create even larger depletion regions inside the germanium-based light absorption material 202, the embodiment shown in FIG. 2E is disclosed. The photo-detecting apparatus 200 e includes N-type regions 207 a, 207 b on the surface 202 ss. The surface 202 ss is opposite to the surface 202 s. With the N-type regions 207 a, 207 b, PN junctions are formed in which a depletion region between P-type region 203 a and N-type region 207 a, and a depletion region between P-type region 203 b and N-type region 207 b, are generated. Consequently, electric fields are created in the absorption region when two different voltages are applied to the control metal lines 206 a, 206 b. Therefore, the said depletion regions/electrical fields can be controlled by control signals cs1, cs2 to control the electron moving direction, either toward N-type region 201 a or N-type region 201 b.

FIG. 2F illustrates a cross-sectional view of a photo-detecting apparatus with body depletion mode, according to some embodiments. The photo-detecting apparatus 200 f includes a wider N-type region 207, which is located underneath the P-type regions 203 a, 203 b. Similarly, the N-type region 207 may enhance the generation of the depletion regions surrounding the P-type regions 203 a, 203 b and therefore increase the quantum efficiency and the demodulation contrast. It is noted that the width of the N-type region 207 is designable, and the width of the N-type region 207 in FIG. 2F is depicted for a reference.

FIG. 2G and FIG. 2H illustrate alternative embodiments showing an approach to bias the N-type region 207. FIG. 2G applies a through-silicon-via (TSV) 204 v to bias the N-type region 207, and FIG. 2G applies a through-germanium-via 202 v extending from surface 202 s to bias N-type region 207.

FIG. 2A to FIG. 2H illustrate a variety of embodiments using body depletion modes, including designing the depth of P-type regions 203 a, 203 b, applying bias voltages vb1, vb2 on either on semiconductor substrate 204 or germanium-based light absorption material 202, adding N-type regions 207, 207 a, 207 b inside the germanium-based light absorption material 202, etc. These approaches create the depletion regions underneath or surrounding the P-type regions 203 a, 203 b to control the moving of the electrons generated from the absorbed photons, either toward N-type region 201 a or N-type region 201 b.

FIGS. 3A-3B illustrate cross-sectional views of a photo-detecting apparatus with gated body depletion mode, according to some embodiments Further to the embodiments illustrated in FIGS. 2A-2H, dielectric-gated body depletion modes are disclosed in FIGS. 3A-3B. The photo-detecting apparatus 300 a includes control metal lines 306 a, 306 b and readout metal lines 308 a, 308 b. The control metal lines 306 a, 306 b and the readout metal lines 308 a, 308 b are electrically coupled to the surface 302 s of the germanium-based light absorption material 302. The control metal lines 306 a, 306 b are respectively electrically coupled to the P-type regions 303 a, 303 b on the surface 302 s, and the readout metal line 308 a, 308 b are respectively electrically coupled to the N-type regions 301 a, 301 b on the surface 202 s. The germanium-based light absorption material 302 is lightly N-type. Furthermore, the photo-detecting apparatus 300 a includes a N-type region 307 on the surface 302 ss, and a dielectric layer 312 formed between the germanium-based light absorption material 302 and the semiconductor substrate 304, and a through silicon via (TSV) 314. In some embodiments, a dielectric layer 312 is arranged between a metal (via 314) and semiconductor (germanium-based light absorption material 302), which forms a MOS-like structure. With the dielectric layer 312 formed between the N-type region 307 and via 314, it may reduce or prevent the electrons from flowing into N-type region 307 to leak through via 314.

In some alternative embodiments, the dielectric layer 312 may not necessarily be continuous layer across the whole semiconductor substrate 304 but can be patterned into different regions located underneath N-type region 307. The dielectric layer 312 may be thin or with some predetermined thickness, including multiple kinds or layers of materials or alloy or compounds, for example, SiO₂, SiN_(x), high-K dielectric material or a combination of thereof.

FIG. 3B illustrates a cross-sectional view of a photo-detecting apparatus with gated body depletion mode, according to some embodiments. This embodiment has no N-type region 307 on the surface 302 ss, but generates the depletion regions 309 a, 309 b through the body bias vb2 and vb3. The body bias vb2 and body bias vb3 may be jointly applied or individually applied to control the size of the depletion regions 309 a, 309 b. The individually applied voltage of the body bias vb2 and the individually applied voltage of body bias vb3 may be the same or different.

Either in FIG. 3A or FIG. 3B, these embodiments insert a dielectric layer 312 between the germanium-based light absorption material 302 and semiconductor substrate 304, and generate the depletion regions (e.g., 309 a, 309 b in FIG. 3B) underneath the P-type regions 303 a, 303 b according to the control signals cs1, cs2 and body bias vb2, vb3 so as to control the electron moving direction inside the germanium-based light absorption material 302. Due to the insertion of the dielectric layer 312, it may reduce or prevent the electrons from flowing into the N-type region 307 (FIG. 3A) and the depletion regions 309 a, 309 b (FIG. 3B) to leak through via 314 (both FIGS. 3A and 3B).

FIG. 4A illustrates a cross-sectional view of a photo-detecting apparatus with a lower leakage current and a lower dark current, according to some embodiments. The photo-detecting apparatus 400 a includes control metal lines 406 a, 406 b and readout metal lines 408 a, 408 b. The control metal lines 406 a, 406 b and the readout metal lines 408 a, 408 b are electrically coupled to the surface 402 s of the germanium-based light absorption material 402 supported by the substrate 404. The control metal lines 406 a, 406 b are respectively electrically coupled to the P-type regions 403 a, 403 b on the surface 402 s, and the readout metal line 408 a, 408 b are respectively electrically coupled to the N-type regions 401 a, 401 b on the surface 402 s. The operation of the apparatus in FIG. 4A is similar to the embodiments disclosed above. The embodiment of FIG. 4A adds N-wells 411 a, 411 b fully surrounding the P-type regions 403 a, 403 b. This may have the effect of reducing the leakage current between P-type regions 403 a, 403 b. In an alternative embodiment, the N-wells 411 a, 411 b can be added partially surrounding the P-type regions 403 a, 403 b as shown in FIG. 4B. This also has the effect of reducing the leakage current between P-type regions 403 a, 403 b.

Further to the embodiments illustrated in FIG. 4A and FIG. 4B, P-wells may be added. The embodiment of FIG. 4C adds P-wells 451 a, 451 b fully surrounding the N-type regions 401 a, 401 b. This may have the effect of reducing the dark currents occurred at N-type regions 401 a, 401 b. In an alternative embodiment, the P-wells 451 a, 451 b can be added partially surrounding the N-type regions 401 a, 401 b as shown in FIG. 4D. This also has the effect of reducing the dark currents occurred at N-type regions 401 a, 401 b.

The embodiments illustrated in FIGS. 4A-4D apply N-wells and P-wells to reduce the leakage current and dark current, respectively. The person skilled in the art can change or modify the patterns of the N-wells 411 a, 411 b and/or P-wells 451 a, 451 b depending on the design requirements. For example, the N-well 411 a can be designed fully surrounding the P-type regions 403 a in an asymmetrical way (e.g., the left-hand side width of the N-well 411 a is wider than the right-hand side width of the N-well 411 a). Similarly, N-well 411 b can also be designed fully surrounding the P-type regions 403 b in an asymmetrical way (e.g., the right-hand side width of the N-well 411 b is wider than the left-hand side width of the N-well 411 b). Similar or modified implementations may also be applied to P-wells 451 a, 451 b.

FIG. 4E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 400 e includes a substrate 404′. The photo-detecting apparatus 400 e further includes a pixel (not labeled) including an absorption layer 402′ supported by the substrate 404′. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 402′. The first switch includes a control contact layer 406 a′ and a readout contact layer 408 a′. The second switch includes a control contact layer 406 b′ and a readout contact layer 408 b′. The control contact layers 406 a′, 406 b′ and the readout contact layers 408 a′, 408 b′ are over the first surface 402 s′ of the absorption layer 402′ along a vertical direction D1. The first switch includes a first doped region 401 a′ under the readout contact layers 408 a′. The second switch includes a first doped region 401 b′ under the readout contact layers 408 b′. The photo-detecting apparatus 400 e includes multiple repeating pixels. The photo-detecting apparatus 400 e includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 408 a′. The second readout circuit is electrically coupled to the readout contact layer 408 b′.

In some embodiments, the first doped regions 401 a′, 401 b′ are of a first conductivity type. In some embodiments, the first doped regions 401 a′, 401 b′ include a first dopant and a dopant profile. The peak dopant concentrations of the first doped regions 401 a′, 401 b′ depend on the material of the readout contact layers 408 a′, 408 b′ and the material of the absorption layer 102′, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 401 a′, 401 b′ are for collecting the carriers generated from the absorption layer 402′, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2.

In some embodiments, the first switch further includes a second doped region 403 a′ under the control contact layers 406 a′. The second switch further includes a second doped region 403 b′ under the control contact layers 406 b′. The second doped regions 403 a′, 403 b′ are formed in the absorption layer 402′ as well. In some embodiments, the second doped regions 403 a′, 403 b′ are of a second conductivity type different from the first conductivity type of the first doped regions 401 b′,401 a′. In some embodiments, the second doped regions 403 a′, 403 b′ include a second dopant and a dopant profile. The peak dopant concentrations of the second doped regions 403 a′, 403 b′ depend on the material of the control contact layers 406 b′, 406 a′ and the material of the absorption layer 402′, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped regions 403 a′, 403 b′ form a Schottky or an Ohmic contact or a combination thereof with the control contact layers 406 b′, 406 a′. The second doped regions 403 a′, 403 b′ are for modulating the carriers generated from the absorption layer 402′ based on the control of the control signals cs1, cs2.

In some embodiments, the pixel further includes two counter-doped regions 411 a′, 411 b′. The counter-doped region 411 a′ overlaps with at least a portion of the second doped region 403 a′. The counter-doped region 411 b′ overlaps with at least a portion of the second doped region 403 b′. In some embodiments, the counter-doped regions 411 a′, 411 b′ are formed in the absorption layer 402′. Each of the counter-doped regions 411 a′, 411 b′ has a conductivity type different from the second conductivity type of the second doped region 403 a′, 403 b′. In some embodiments, the photo-detecting apparatus 400 e is configured to process the collected holes for further application. In such an embodiment, the first doped regions 401 b′, 401 a′ are of p-type, the second doped region 403 a′, 403 b′ are of n-type, and the counter-doped regions 411 b′, 411 a′ are of p-type. In some embodiments, the counter-doped region 411 b′ overlaps with at least a portion of the second doped region 403 b′ nearer the first doped regions 401 b′. In some embodiments, at least a portion of the counter-doped region 411 b′ is between the first doped regions 401 b′ and the second doped region 403 b′. In some embodiments, the counter-doped region 411 a′ overlaps with at least a portion of the second doped region 403 a′ nearer the first doped regions 401 a′. In some embodiments, at least a portion of the counter-doped region 411 a′ is between the first doped regions 401 a′ and the second doped region 403 a′.

In some embodiments, the counter-doped regions 411 a′, 411 b′ serve as dark-current reduction regions for reducing the dark current of the photo-detecting apparatus 400 e. Compared to a photo-detecting apparatus devoid of counter-doped regions 411 a′, 411 b′, the photo-detecting apparatus 400 e including counter-doped regions 411 a′, 411 b′ overlapping at least a portion of the second doped regions 403 a′, 403 b′ has thinner depletion regions, and thus the photo-detecting apparatus 400 e is with lower dark current.

In some embodiments, each of the counter-doped regions 411 a′, 411 b′ includes a dopant, and each of the counter-doped regions 411 a′, 411 b′ has a dopant profile with a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁶ cm⁻³. In some embodiment, the peak dopant concentrations of the counter-doped regions 411 a′, 411 b′ are lower than the peak dopant concentrations of the second doped regions 403 b′, 403 a′. In some embodiments, the peak dopant concentration of each of the counter-doped regions 411 a′, 411 b′ is between 1×10¹⁶ cm⁻³ and 1×10¹⁸ cm⁻³.

FIG. 4F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 400 f in FIG. 4F is similar to the photo-detecting apparatus in FIG. 4E, where the difference is described below. In some embodiments, the photo-detecting apparatus 400 f further includes a blocking layer 419 surrounding at least a portion of the absorption layer 402′, wherein the blocking layer 419 is of a conductivity type different from the first conductivity type of each of the first doped regions 401 b′, 401 a′. The blocking layer 419 may block photo-generated charges in the absorption layer 402′ from reaching the substrate 404′, which increases the collection efficiency of photo-generated carriers of the photo-detecting apparatus 400 f The blocking layer 419 may also block photo-generated charges in the substrate 404′ from reaching the absorption layer 402′, which increases the speed of photo-generated carriers of the photo-detecting apparatus 400 f. The blocking layer 419 may include a material the same as the material of the absorption layer 402′, the same as the material of the substrate 404′, a material as a combination of the material of the absorption layer 402′ and the material of the substrate 404′, or different from the material of the absorption layer 402′ and the material of the substrate 404′. In some embodiments, the shape of the blocking layer 419 may be but not limited to a ring. In some embodiments, the blocking layer 419 includes a dopant and has a dopant profile with a peak dopant concentration ranging from 10¹⁵ cm⁻³ to 10²⁰ cm⁻³. The blocking layer 419 may reduce the cross talk between two adjacent pixels.

In some embodiments, the blocking layer 419 extends to reach the first surface 404 s of the substrate 404′. In some embodiments, photo-detecting apparatus 400 f may further include a conductive layer 409 electrically connected to the blocking layer 419. The blocking layer 419 may be biased through the conductive layer 409 by a bias voltage ca2 to discharge carriers not collected by the first doped regions 401 a′, 401 b′.

In some embodiments, the photo-detecting apparatus 400 f is configured to process the collected holes for further application. In such an embodiment, the first doped regions 401 b′, 401 a′ are of p-type, the second doped region 403 a′, 403 b′ are of n-type, and the counter-doped regions 411 b′, 411 a′ are of p-type, and the blocking layer 419 is of n-type.

FIG. 4G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 400 g in FIG. 4G is similar to the photo-detecting apparatus 400 e in FIG. 4E, where the difference is described below. The first doped regions 401 b′, 401 a′ are formed in the substrate 404′. The readout contact layers 408 a′, 408 b′ are formed over the first surface 404 s of the substrate 404′. A distance d₃ between the control contact layers 406 a′, 406 b′ is less than a width w₃ of the absorption layer 402′. In some embodiments, a distance d₄ between the readout contact layers 408 a′, 408 b′ is greater than the width w₃ of the absorption layer 402′. In some embodiments, since the dark current of the substrate 404′ is lower than the dark current of the absorption layer 402′, by disposing the first doped regions 401 b′, 401 a′ in the substrate 404′ can further reduce the dark current of the photo-detecting apparatus 400 g.

FIG. 4H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 400 h in FIG. 4H is similar to the photo-detecting apparatus 400 g in FIG. 4G, where the difference is described below. The second doped regions 403 b′, 403 a′ are formed in the substrate 404′. The control contact layers 406 a′, 406 b′ are formed over the first surface 404 s of the substrate 404′. In some embodiments, the counter-doped regions 411 a′, 411 b′ are formed in the substrate 404′. A distance d₃ between the control contact layers 406 a′, 406 b′ is greater than a width w₃ of the absorption layer 402′. In some embodiments, since the dark current of the substrate 404′ is lower than the dark current of the absorption layer 402′, by disposing the first doped regions 401 b′, 401 a′, the second doped regions 403 b′,403 a′ and the counter-doped regions 411 a′, 411 b′ in the substrate 404′ can further reduce the dark current of the photo-detecting apparatus 400 h.

FIG. 5A illustrates a cross-sectional view of a photo-detecting apparatus with passivation layer, according to some embodiments. The photo-detecting apparatus 500 a includes control metal lines 506 a, 506 b and readout metal lines 508 a, 508 b. The control metal lines 506 a, 506 b and the readout metal lines 508 a, 508 b are electrically coupled to the surface 502 s of the germanium-based light absorption material 502 supported by the substrate 504. The control metal lines 506 a, 506 b are respectively electrically coupled to the P-type regions 503 a, 503 b on the surface 502 s, and the readout metal lines 508 a, 508 b are respectively electrically coupled to the N-type regions 501 a, 501 b on the surface 502 s. The embodiment of FIG. 5A adds a passivation layer 514 (e.g., amorphous-silicon (a-Si), GeO_(x), Al₂O₃, SiO₂) over the surface 502 s, adds a silicide (e.g., NiSi₂, CoSi₂) 513 a at the connection between the readout metal line 508 a and the N-type region 501 a, adds a silicide 513 b at the connection between the readout metal line 508 b and the N-type region 501 b, adds a silicide 515 a at the connection between the control metal line 506 a and the P-type region 503 a, and adds a silicide 515 b at the connection between the control metal line 506 b and the P-type region 503 b.

In accordance with this embodiment, forming the passivation layer 514 over the germanium-based light absorption material 502 can terminate the dangling bonds on the surface 502 s and so reduce the dark currents. On the other hand, adding the silicide (e.g., NiSi₂, CoSi₂) can also reduce the contact or junction resistance between the metal and semiconductor, which reduces the voltage drop and reduces power consumption accordingly.

In some embodiments, the passivation layer 514 is intrinsic. The term “intrinsic” means that the passivation layer 514 is without intentionally adding dopants. In some embodiments, a method for manufacturing the photo-detecting apparatus 500 a includes steps of forming the N-type regions 501 a,501 b; forming the P-type region 503 a, 503 b; forming the passivation layer 514 over the surface 502 s of the germanium-based light absorption material 502; and forming silicide 515 a, 515 b, 513 a,513 b in the passivation layer 514; wherein the step of forming the passivation layer 514 over the surface 502 s of the germanium-based light absorption material 502 is after the step of forming the N-type regions 501 a,501 b, and the step of forming the P-type region 503 a, 503 b.

FIG. 5B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 b includes a substrate 504′. The photo-detecting apparatus further includes a pixel (not labeled) including an absorption layer 502′ supported by the substrate 504′. The pixel includes an absorbed region AR in the absorption layer 502′. The absorbed region AR is a virtual area receiving an incoming optical signal. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 502′. The first switch includes a control contact layer 506 a′ and a readout contact layer 508 a′. The second switch includes a control contact layer 506 b′ and a readout contact layer 508 b′. In some embodiments, the readout contact layers 508 a′, 508 b′, and the control contact layers 506 a′, 506 b′ are on a first surface 502 s′ of the absorption layer 502′. In some embodiments, a width of the absorbed region AR is less than a distance between the readout contact layers 508 a′, 508 b′. In some embodiments, the readout contact layers 508 a′, 508 b′ are disposed at two opposite sides of the absorbed region AR. In some embodiments, a width of the absorbed region AR is less than a distance between the control contact layers 506 a′, 506 b′. In some embodiments, the control contact layers 506 a′, 506 b′ are disposed at two opposite sides of the absorbed region AR. In some embodiments, the photo-detecting apparatus 500 b includes multiple repeating pixels. The photo-detecting apparatus 500 b includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

The pixel further includes two control signals cs1, cs2 controlling the control contact layers 506 a′, 506 b′ for controlling the moving direction of the electrons or holes generated by the absorbed photons in the absorption layer 502′. For example, when voltages are used, if the control signal cs1 is biased against the control signal cs2, an electric field is created between the two portions right under the control contact layers 506 a′, 506 b′, and free charges drift towards one of the two portions right under the readout contact layers 508 b′ 508 a′ depending on the direction of the electric field.

In some embodiments, the pixel includes two capacitors (not shown). The readout contact layers 508 a′ is electrically coupled to one of the capacitors, and the readout contact layers 508 b′ is electrically coupled to the other capacitor. The capacitors are for storing the carriers generated in the absorption layer 502′ based on the control of the two control signals cs1, cs2. For example, due to a distance existing between the photo-detecting apparatus 500 b and a target object (not shown), an optical signal has a phase delay with respect to a transmitted light transmitted by a transmitter (not shown). When the transmitted light is modulated by a modulation signal and the electron-hole pairs are demodulated through the control contact layers 506 a′, 506 b′ by a demodulation signal, the electrons or the holes stored in the capacitors will be varied according to the distance. Therefore, the photo-detecting apparatus 500 b can obtain the distance information based on the voltage v1 on one of the capacitors and the voltage v2 on the other capacitor.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit may include one of the capacitors. The second readout circuit may include the other capacitor. The first readout circuit is electrically coupled to the readout contact layer 508 a′. The second readout circuit is electrically coupled to the readout contact layer 508 b′.

In some embodiments, the first switch includes a first doped region 501 a′ under the readout contact layers 508 a′. The second switch includes a first doped region 501 b′ under the readout contact layers 508 b′. In some embodiments, the first doped regions 501 a′, 501 b′ are of a first conductivity type. In some embodiments, each of the first doped regions 501 a′, 501 b′ includes a first dopant and a dopant profile. The peak dopant concentrations of the first doped regions 501 a′, 501 b′ depend on the material of the readout contact layers 508 a′, 508 b′ and the material of the absorption layer 502′, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 501 a′, 501 b′ are for collecting the carriers generated from the absorption layer 502′, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2.

In some embodiments, the first switch further includes a second doped region 503 a′ under the control contact layers 506 a′. The second switch further includes a second doped region 503 b′ under the control contact layers 506 b′. The second doped regions 503 a′, 503 b′ are formed in the absorption layer 502′. In some embodiments, the second doped regions 503 a′, 503 b′ are each of a second conductivity type different from the first conductivity type of the first doped regions 501 b′, 501 a′. In some embodiments, each of the second doped regions 503 a′, 503 b′ includes a second dopant and a dopant profile. The peak dopant concentrations of the second doped regions 503 a′, 503 b′ depend on the material of the control contact layers 506 b′, 506 a′ and the material of the absorption layer 502′, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped regions 503 a′, 503 b′ forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 506 b′, 506 a′. The second doped regions 503 a′, 503 b′ are for demodulating the carriers generated and flow from the absorption layer 502′ based on the control of the control signals cs1, cs2.

In some embodiments, the pixel further includes a passivation layer 514 over a first surface 502 s′ of the absorption layer 502′. In some embodiments, the passivation layer 514 further covers a portion of the first surface 504 s of the substrate 504. In some embodiments, the absorption layer 502′ is protruded from the first surface 504 s of the substrate 504′, and the passivation layer 514 further covers a sidewall of the absorption layer 502′ exposed from the substrate 504′. The passivation layer 514 may include amorphous silicon, poly silicon, epitaxial silicon, aluminum oxide (e.g., Al_(x)O_(y)), silicon oxide (e.g., Si_(x)O_(y)), Ge oxide (e.g., Ge_(x)O_(y)), germanium-silicon (e.g., GeSi), silicon nitride family (e.g., Si_(x)N_(y)), high-k materials (e.g. HfO_(x), ZnO_(x), LaO_(x), LaSiO_(x)), and any combination thereof. The presence of the passivation layer 514 may have various effects. For example, the passivation layer 514 may act as a surface passivation layer to the absorption layer 502′, which may reduce dark current or leakage current generated by defects occurred at the exposed surface of the absorption layer 502′. In some embodiments, the passivation layer 514 has a thickness not more than 100 nm. In some embodiments, a part of the first doped regions 501 a′, 501 b′ may be formed in the portions of the passivation layer 514 between the absorption layer 502′ and the readout contact layers 508 a′, 508 b′ respectively. That is, the first dopants of the first doped regions 501 a′, 501 b′ may be in the portions of the passivation layer 514 between the absorption layer 502′ and the readout contact layers 508 a′, 508 b′ respectively. In some embodiments, a part of the second doped regions 503 a′, 503 b′ may be formed in the portions of the passivation layer 514 between the absorption layer 502′ and the control contact layer 506 a′, 506 b′ respectively. That is, the second dopants of the second doped regions 503 a′, 503 b′ may be in the portions of the passivation layer 514 between the absorption layer 502′ and the control contact layer 506 a′, 506 b′ respectively.

In some embodiments, the pixel further includes first silicide regions 513 a′, 513 b′ between the first doped regions 501 a′, 501 b′ and the readout contact layers 508 a′, 508 b′. In some embodiments, the pixel further includes second silicide regions 515 a′, 515 b′ between the second doped regions 503 a′, 503 b′ and the control contact layer 506 a′, 506 b′. The first silicide regions 513 a′, 513 b′ and the second silicide regions 515 a′, 515 b′ include M_(x)Si_(y), wherein M is metal, x and y are the number of metal and silicon atoms respectively. In some embodiments, M includes, but is not limited to Ni, Co, Ti, W, Cr, Ta, Pt or a combination thereof. The first silicide regions 513 a′, 513 b′ can reduce the contact or junction resistance between the readout contact layers 508 a′, 508 b′ and the absorption layer 502′. The second silicide regions 515 a′, 515 b′ can reduce the contact or junction resistance between the control contact layer 506 a′, 506 b′ and the absorption layer 502′. As a result, the voltage drop and the power consumption of the photo-detecting apparatus 500 b can be reduced.

In some embodiments, a method for manufacturing the photo-detecting apparatus 500 b includes steps of forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′; forming the first doped regions 501 a′, 501 b′ in the absorption layer 502′ and the passivation layer 514; forming the second doped regions 503 a′, 503 b′ in the absorption layer 502′ and the passivation layer 514; forming the first silicide regions 513 a′, 513 b′ and the second silicide regions 515 a′, 515 b′ in the passivation layer 514. In some embodiments, the step of forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′ is before the step of forming the first doped regions 501 a′, 501 b′, and the step of forming the second doped regions 503 a′, 503 b′.

FIG. 5C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 c in FIG. 5C is similar to the photo-detecting apparatus in FIG. 5B, where the difference is described below. In some embodiments, the passivation layer 514 includes at least two regions with different properties. For example, as shown in FIG. 5C, the passivation layer 514 includes four first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4 separated from each other. The first region 514 a 1 is between the first doped regions 501 b′ and the readout contact layer 508 b′. In some embodiments, first region 514 a 1 is between the first doped region 501 b′ and the first silicide region 513 b′. The first region 514 a 2 is between the second doped regions 503 b′ and the control contact layer 506 b′. In some embodiments, first region 514 a 2 is between the second doped regions 503 b′ and the second silicide region 515 b′. The first region 514 a 3 is between the first doped region 501 a′ and the readout contact layer 508 a′. In some embodiments, first region 514 a 3 is between the first doped regions 501 a′ and the first silicide region 513 a′. The first region 514 a 4 is between the second doped regions 503 a′ and the control contact layer 506 a′. In some embodiments, first region 514 a 4 is between the second doped regions 503 a′ and the second silicide region 515 a′. The passivation layer 514 further includes a second region 514 b between and separating the two first regions 514 a 2, 514 a 4.

Each of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4 includes a property. The second region 514 b includes a property different from the property of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the property includes material or resistance. For example, the second region 514 b has a resistance higher than that of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the second region 514 b includes an insulating material. For example, the insulating material includes an insulating oxide material or an insulating nitride material. The insulating oxide material includes, but is not limited to, aluminum oxide (e.g., Al_(x)O_(y)), silicon oxide (e.g., Si_(x)O_(y)), Ge oxide (e.g., Ge_(x)O_(y)), HfO_(x), ZnO_(x), LaO_(x), LaSiO_(x) or any combination thereof. The insulating nitride material includes, but is not limited to silicon nitride family (e.g., Si_(x)N_(y)), germanium nitride family (e.g., Ge_(x)N_(y)). In some embodiments, the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. include a semiconductor material including, but not limited to, amorphous silicon, poly silicon, epitaxial silicon, germanium-silicon (e.g., GeSi), or any combination thereof. The second region 514 b can block the electrical conduction between the second doped regions 503 a′, 503 b′ through the passivation layer 514 and also block the electrical conduction between the second doped regions 503 a′, 503 b′ along the interface between the passivation layer 514 and the absorption layer 502′. As a result, the leakage current between the second doped regions 503 a′, 503 b′ can be reduced. In some embodiments, the passivation layer 514 further includes two third regions 514 c from the cross-sectional view of the photo-detecting apparatus 500 c. The third regions 514 c cover a periphery part of the first surface 502 s′ of the absorption layer 502′. In some embodiments, each of the two third regions 514 c includes a property different from the property of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. For example, each of the third regions 514 c has a resistance higher than that of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the third regions 514 c include an insulating material. In some embodiments, the third regions 514 c and the second region 514 b may be a continuous region surrounding the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the third regions 514 c are discrete regions and also separated from the second region 514 b. In some embodiments, the material of the third regions 514 c and the material of the second region 514 b may be the same. The third regions 514 c may further block the electrical conduction between the first doped regions 501 a′, 501 b′ through the periphery part of the passivation layer 514 and also block the electrical conduction between the first doped regions 501 a′, 501 b′ along the interface of the periphery part between the passivation layer 514 and the absorption layer 502′. In some embodiments, the passivation layer 514 further includes two fourth regions 514 e from the cross-sectional view of the photo-detecting apparatus 500 c. The fourth regions 514 e are between two of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, each of the two fourth regions 514 e includes a property different from the property of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. For example, the fourth region 514 e has a resistance higher than that of the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the fourth regions 514 e include an insulating material. In some embodiments, the fourth regions 514 e, the third regions 514 c and the second region 514 b may be a continuous region surrounding the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. In some embodiments, the fourth regions 514 e are discrete regions and also separated from the second region 514 b and the third region 514 c. In some embodiments, the material of the fourth regions 514 e, the material of the third regions 514 c and the material of the second region 514 b may be the same. The fourth regions 514 e may further block the electrical conduction between the first doped regions 501 a′, 501 b′ through the part of the passivation layer 514 between the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4. As a result, the leakage current is further reduced. In some embodiments, the first regions 514 a 1, 514 a 2, 514 a 3, 514 a 4 are conductive regions. The second region 514 b, the third region 514 c and the fourth regions 514 d are insulating regions.

In some embodiments, each of the second doped regions 503 a′, 503 b′ includes a depth d1. Each of the first doped regions 501 a′, 501 b′ includes a depth d2. The depth d1 of each of the second doped regions 503 a′, 503 b′ is greater than the depth d2 of each of the first doped regions 501 a′, 501 b′. In some embodiments, the ratio of the depth d1 to the depth d2 is not less than 1.5. In some embodiments, the depth d1 is measured from the first surface 502 s′ of the absorption layer 502′ to the position where the second dopant is of a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the depth d2 is measured from the first surface 502 s′ of the absorption layer 502′ to the position where the first dopant is of a background concentration, such as 1×10¹⁵ cm⁻³. Since the depth d1 of each of the second doped regions 503 a′, 503 b′ is greater than the depth d2 of each of the first doped regions 501 a′, 501 b′, the modulation bandwidth can be kept satisfied.

FIG. 5D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 d in FIG. 5D is similar to the photo-detecting apparatus in FIG. 5B, where the difference is described below. The photo-detecting apparatus 500 d may be devoid of second doped regions 503 a′, 503 b′. That is, the regions of the absorption layer 502′ right under the control contact layers 506 a′, 506 b′ may be intrinsic or include a dopant and has a dopant profile with a peak dopant concentration below approximately 1×10¹⁵ cm⁻³. The term “intrinsic” means that the regions of the semiconductor material, such as the absorption layer 502′ and/or the passivation layer 514 right under the control contact layers 506 a′, 506 b′ are without intentionally adding dopants. In some embodiments, the control contact layers 506 a′, 506 b′ on the absorption layer 502′ may lead to formation of a Schottky contact, an Ohmic contact, or a combination thereof having an intermediate characteristic between the two, depending on various factors including the material of the absorption layer 502′, the material of the control contact layers 506 a′, 506 b′, the material of the passivation layer 514, the material of the second silicide regions 515 a′, 515 b′, and the impurity or defect level of the absorption layer 502′.

FIG. 5E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 e in FIG. 5E is similar to the photo-detecting apparatus 500 c in FIG. 5C, where the difference is described below. The photo-detecting apparatus 500 e may be devoid of the second doped regions 503 a′, 503 b′, which is similar to described in FIG. 5D.

FIG. 5F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 f in FIG. 5F is similar to the photo-detecting apparatus 500 b in FIG. 5B, where the difference is described below. The passivation layer 514 includes two intermediate regions 514 d 1, 514 d 2 separated from each other. The intermediate region 514 d 1 is between second doped region 503 a′ and the control contact layers 506 a′. In some embodiments, the passivation layer 514 includes semiconductor material. In some embodiments, the intermediate region 514 d 1 is between second doped region 503 a′ and the second silicide regions 515 a′. The intermediate region 514 d 2 is between second doped region 503 b′ and the control contact layers 506 b′. In some embodiments, the intermediate region 514 d 2 is between second doped region 503 b′ and the second silicide regions 515 b′. In some embodiments, the intermediate regions 514 d 1, 514 d 2 may be intrinsic. In some embodiments, the intermediate regions 514 d 1, 514 d 2 is of a conductivity type the same or different from the second conductivity type of the second doped regions 503 a′, 503 b′. In some embodiments, each of the intermediate regions 514 d 1, 514 d 2 includes a dopant and a dopant profile. The peak dopant concentrations of the intermediate regions 514 d 1, 514 d 2 is less than the peak dopant concentrations of the second doped regions 503 a′, 503 b′. In some embodiments, the peak dopant concentrations of the intermediate regions 514 d 1, 514 d 2 is between 5×10¹⁶ cm⁻³ to 5×10¹⁷ cm⁻³. Since the peak dopant concentrations of the intermediate regions 514 d 1, 514 d 2 is less than the peak dopant concentrations of the second doped regions 503 a′, 503 b′, the intermediate regions 514 d 1, 514 d 2 can block the electrical conduction between the second doped regions 503 a′,503 b′ through the passivation layer 514 and also block the electrical conduction between the second doped regions 503 a′, 503 b′ along the interface between the passivation layer 514 and the absorption layer 502′.

In some embodiments, a method for manufacturing the photo-detecting apparatus 500 f includes steps of forming the first doped regions 501 a′, 501 b′; forming the second doped regions 503 a′, 503 b′ in the absorption layer 502′; forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′.

In some embodiments, the step of forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′ includes forming a semiconductor layer over the first surface 502 s′ of the absorption layer 502′; and forming the intermediate regions 514 d 1, 514 d 2 in the semiconductor layer by any suitable method, such as doping dopants in the part of the semiconductor layer over the second doped regions 503 a′, 503 b′ respectively.

In some embodiments, the method for manufacturing the photo-detecting apparatus 500 f further includes forming the first silicide regions 513 a′, 513 b′ and the second silicide regions 515 a′, 515 b′ in the passivation layer 514.

In some embodiments, the step of forming the first doped regions 501 a′, 501 b′ includes doping a first dopant in the absorption layer 502′ before the step of forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′. In some embodiments, the step of forming the first doped regions 501 a′, 501 b′ further includes doping a first dopant in the passivation layer 514 after the step of forming the passivation layer 514 over the first surface 502 s′ of the absorption layer 502′.

FIG. 5G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 g in FIG. 5G is similar to the photo-detecting apparatus 500 c in FIG. 5C, where the difference is described below. The passivation layer 514 includes two intermediate regions 514 d 1, 514 d 2 similar to the intermediate regions 514 d 1, 514 d 2 described in FIG. 5F. By the combination of the second region 514 b and the intermediate regions 514 d 1, 514 d 2, the leakage current between the second doped regions 503 a′ 503 b′ can be further reduced.

FIG. 5H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 500 h in FIG. 5H is similar to the photo-detecting apparatus 500 g in FIG. 5G, where the difference is described below. The photo-detecting apparatus 500 h further includes a blocking layer 519 surrounding at least a portion of the absorption layer 502′. In some embodiments, the blocking layer 519 is of a conductivity type the same as a conductivity type of the absorption layer 502′. The blocking layer 519 may block photo-generated charges in the absorption layer 502′ from reaching the substrate 504′, which increases the collection efficiency of photo-generated carriers of the photo-detecting apparatus 500 h. The blocking layer 519 may also block photo-generated charges in the substrate 504′ from reaching the absorption layer 502′, which increases the speed of photo-generated carriers of the photo-detecting apparatus 500 h. The blocking layer 519 may include a material the same as the material of the absorption layer 502′, the same as the material of the substrate 504′, a material as a combination of the material of the absorption layer 502′ and the material of the substrate 504′, or different from the material of the absorption layer 502′ and the material of the substrate 504′. In some embodiments, the shape of the blocking layer 519 may be but not limited to a ring. In some embodiments, the blocking layer 519 may reach the first surface 504 s of the substrate 504′. In some embodiments, the blocking layer 519 includes a dopant and has a dopant profile with a peak dopant concentration ranging from 1×10¹⁵ cm⁻³ to 1×10²⁰ cm⁻³. The blocking layer 519 may reduce the cross talk between two adjacent pixels.

In some embodiments, the photo-detecting apparatus 500 h further includes a conductive layer (not shown) electrically connected to the blocking layer 519. The blocking layer 519 may be biased through the conductive layer by a bias voltage to discharge carriers not collected by the first doped regions 501 a′, 501 b′.

FIG. 6A illustrates a cross-sectional view of a photo-detecting apparatus with boosted charge transfer speed, according to some embodiments. The photo-detecting apparatus 600 a includes control metal lines 606 a, 606 b and readout metal lines 608 a, 608 b. The control metal lines 606 a, 606 b and the readout metal lines 608 a, 608 b are electrically coupled to the surface 602 s of the germanium-based light absorption material 602. The control metal lines 606 a, 606 b are respectively electrically coupled to the P-type regions 603 a, 603 b on the surface 602 s, and the readout metal line 608 a, 608 b are respectively electrically coupled to the N-type regions 601 a, 601 b on the surface 602 s. The embodiment of FIG. 6A adds an N-type region 617 on the surface 602 s and a P-type region 619 on the surface 602 ss. The N-type region 617 and P-type region 619 are formed substantially on the center of the germanium-based light absorption material 602, which is a location that the optical signal IL may pass through. Due to the fact that the N-type region 617 and P-type region 619 are collectively formed as a PN-junction, there are built-in vertical electrical fields established between N-type region 617 and P-type region 619, which may assist separating the electron-hole pairs generated by the absorbed photons, where the electrons tends to move toward the N-type region 617 and the holes tends to move toward the P-type region 619. The N-type region 617 is operated to collect the electrons and the P-type region 619 is operated to collect the holes. The electrons stored in the N-type region 617 may be moved to N-type region 601 a or N-type region 601 b according to the control signals cs1, cs2. Notably, the metal line 610 can be floating or be biased by a bias voltage ca1 depending on the operation of photo-detecting apparatus 600 a. In one implementation, doping concentration of the N-type regions 601 a, 601 b are higher than a doping concentration of the N-type region 617.

FIG. 6B illustrates a cross-sectional view of a photo-detecting apparatus with boosted charge transfer speed, according to some embodiments. This embodiment is similar to the photo-detecting apparatus 600 a. The difference is that the P-type region 619 can be biased though a silicon via 604 v, in which the holes collected in the P-type region 619 can be discharged through the silicon via 604 v, which is biased by a bias voltage ca2 thereon.

FIG. 6C illustrates a cross-sectional view of a photo-detecting apparatus with boosted charge transfer speed, according to some embodiments. The embodiment of FIG. 6C is similar to the photo-detecting apparatus 600 b. The difference is that a P-type region 619 is formed as a U-shape or a well-shape underneath and surrounding the germanium-based light absorption material 602. Also, this P-type region 619 is electrically coupled to a bias voltage ca2. Therefore, the photo-generated holes can be collected and discharged by the P-type region 619.

FIG. 6D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 d includes a substrate 604′. The photo-detecting apparatus further includes a pixel (not labeled) including an absorption layer 602′ supported by a substrate 604′. The pixel includes an absorbed region AR in the absorption layer 602′ and defined by a light shield (not shown). The absorption layer 602′ includes a first surface 602 s′ and a second surface 602 ss′ opposite to the first surface 602 s′. The absorbed region AR is a virtual area receiving an optical signal incoming through an optical window of the light shield. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 602′. The first switch includes a control contact layer 606 a′ and a readout contact layer 608 a′. The second switch includes a control contact layer 606 b′ and a readout contact layer 608 b′. In some embodiments, the readout contact layers 608 a′, 608 b′ are on a first surface 604 s of the substrate 604′. In some embodiments, the readout contact layers 608 a′, 608 b′ are disposed at two opposite sides of the absorbed region AR. In some embodiments, a width of the absorbed region AR is less than a distance d3 between the control contact layers 606 a′, 606 b′. In some embodiments, the control contact layers 606 a′, 606 b′ are disposed at two opposite sides of the absorbed region AR. In some embodiments, the first surface 602 s′ of the absorption layer 602′ is substantially flush with the first surface 604 s of the substrate 604′. The photo-detecting apparatus 600 d includes multiple repeating pixels. The photo-detecting apparatus 600 d includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the control contact layers 606 a′, 606 b′ are on both of the first surface 604 s of the substrate 604′ and the first surface 602 s′ of the absorption layer 602′. In other words, a part of the control contact layers 606 a′, 606 b′ is over the first surface 604 s′ of the substrate 604′ and the other part of the control contact layers 606 a′, 606 b′ is over the first surface 602 s′ of the absorption layer 602′. In some embodiments, the control contact layers 606 a′, 606 b′ are on a part of the interface between the substrate 604′ and the absorption layer 602′. In some embodiments, a distance d₃ between the control contact layers 606 a′, 606 b′ is less than a width w₃ of the absorption layer 602′. In some embodiments, a distance d₄ between the readout contact layers 608 a′, 608 b′ is greater than the width w₃ of the absorption layer 602′.

In some embodiments, un-doped regions 605 a, 605 b are right under the control contact layers 606 a′, 606 b′. That is, the portions of the absorption layer 602′ and the substrate 604′ right under the control contact layers 606 a′, 606 b′ may be intrinsic or include a dopant and has a dopant profile with a peak dopant concentration below approximately 1×10¹⁵ cm⁻³. The term “intrinsic” means that the portions of the semiconductor material right under the control contact layers 606 a′, 606 b′ are without intentionally adding dopants. In some embodiments, the control contact layers 606 a′, 606 b′ on the absorption layer 602′ and the substrate 604′ may lead to formation of a Schottky contact, an Ohmic contact, or a combination thereof having an intermediate characteristic between the two, depending on various factors including the material of the absorption layer 602′, the material of the substrate 604′, the material of the control contact layers 606 a′, 606 b′, and the impurity or defect level of the absorption layer 602′ as well as the substrate 604′.

The pixel further includes two control signals cs1, cs2 controlling the control contact layers 606 a′, 606 b′ for controlling the moving direction of the electrons or holes generated by the absorbed photons in the absorption layer 602′. For example, when voltages are used, if the control signal cs1 is biased against the control signal cs2, an electric field is created between the two portions right under the control contact layers 606 a′, 606 b′, and free charges drift towards one of the two portions right under the readout contact layers 608 b′ 608 a′ depending on the direction of the electric field.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 608 a′. The second readout circuit is electrically coupled to the readout contact layer 608 b′.

In some embodiments, the first switch includes a first doped region 601 a′ under the readout contact layers 608 a′. The second switch includes a first doped region 601 b under the readout contact layers 608 b′.

In some embodiments, the first doped regions 601 a′, 601 b′ are of a first conductivity type. In some embodiments, each of the first doped regions 601 a′, 601 b′ include a first dopant and a dopant profile. The peak dopant concentrations of the first doped regions 601 a′, 601 b′ depend on the material of the readout contact layers 608 a′, 608 b′ and the material of the absorption layer 602′, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 601 a′, 601 b′ are for collecting the carriers generated from the absorbed region AR in the absorption layer 602′, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2.

The pixel of the photo-detecting apparatus 600 d further includes a third doped region 617′ in the absorption layer 602′. The third doped region 617′ is of a third conductivity type the same as the first conductivity type of the first doped regions 601 a′, 601 b′. The pixel of the photo-detecting apparatus 600 d further includes a fourth doped region 618 in the absorption layer 602′. In some embodiments, the fourth doped region 618 is between the third doped region 617′ and the second surface 602 ss′. In some embodiments, the third doped region 617′ includes a third dopant and has a dopant profile with a peak between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³. The peak dopant concentration of the third doped region 617′ is closer to the first surface 602 s′ of the absorption layer 602′ than the second surface 602 ss′ of the absorption layer 602′. In some embodiments, a distance between a location of the third doped region 617′ having the peak dopant concentration and the first surface 602 s′ of the absorption layer 602′ is not more than 50 nm. In some embodiments, the fourth doped region 618 includes a fourth dopant and is of a fourth conductivity type different from the third conductivity type of the third doped region 617′. In some embodiments, the fourth doped region 618 includes a fourth dopant and has a dopant profile with a peak dopant concentration between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³. The peak dopant concentration of the fourth doped region 618 is closer to the second surface 602 ss′ of the absorption layer 602′ than the first surface 602 s′ of the absorption layer 602′.

Since the third doped region 617′ and fourth doped region 618 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between third doped region 617′ and fourth doped region 618, which may assist in separating the electron-hole pairs generated by the absorbed photons, for example, when the third doped region 617′ is of n-type and the fourth doped region 618 is of p-type, the electrons tends to move toward the third doped region 617′ and the holes tends to move toward the fourth doped region 618. The third doped region 617′ is operated to collect the electrons and the fourth doped region 618 is operated to collect the holes. The electrons stored in the third doped region 617′ may be moved to first doped region 601 b′ or the first doped region 601 a′ based on the control signals cs1, cs2. Therefore, the quantum efficiency of the photo-detecting apparatus 600 d is higher and the amount of the carriers moving toward the first doped region 601 b′ or the first doped region 601 a′ is also higher.

In some embodiment, the photo-detecting apparatus 600 d further includes an isolation region 624 at least disposed at two opposite sides of the absorption layer 602′ from a cross-sectional view of the photo-detecting apparatus 600 d. The isolation region 624 is in the substrate 604′ and physically separated from the absorption layer 602′. In some embodiments, the isolation region 624 is a trench filled with a dielectric material or an insulating material to serve as a region of high electrical resistance between the two adjacent pixels, impeding a flow of current across the isolation region 624 and improving electrical isolation between the adjacent pixels. The dielectric material or an insulating material may include, but is not limited to oxide material including SiO₂ or nitride material including Si₃N₄ or silicon material including amorphous-Si, poly-Si, monocrystalline-Si or epitaxial-Si.

In some embodiments, the isolation region 624 extends from a first surface 604 s of the substrate 604′ and extends into a predetermined depth from the first surface 604 s. In some embodiments, the isolation region 624 extends from a second surface 604 ss of the substrate 604′ and extends into a predetermined depth from the second surface 604 ss. In some embodiments, the isolation region 624 penetrates though the substrate 604′ from the first surface 604 s to the second surface 604 ss.

In some embodiments, the isolation region 624 is a doped region having a conductivity type. The conductivity type of the isolation region 624 can be different from or the same as the first conductivity type of the first doped regions 601 a′, 601 b′. The doping of the isolation region 624 may create a bandgap offset-induced potential energy barrier that impedes a flow of current across the isolation region 624 and improving electrical isolation between the adjacent pixels. In some embodiments, the isolation region 624 includes a semiconductor material that is different from the material of the substrate 604′. An interface between two different semiconductor materials formed between the substrate 604′ and the isolation region 624 may create a bandgap offset-induced energy barrier that impedes a flow of current across the isolation region 624 and improving electrical isolation between the adjacent pixels. In some embodiments, the shape of the isolation region 624 may be a ring. In some embodiments, the isolation region 624 may include two discrete regions disposed at the two opposite sides of the absorption layer 602′.

In some embodiments, the photo-detecting apparatus 600 d further includes a conductive layer 610′ on the first surface 602 s′ of the absorption layer 602′. The conductive layer 610′ is on the third doped region 617′. The conductive layer 610′ can be floating or be biased by a bias voltage ca1 depending on the operation of photo-detecting apparatus 600 d.

FIG. 6E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 e in FIG. 6E is similar to the photo-detecting apparatus 600 d in FIG. 6D, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped region 603 b′ under the control contact layers 606 b′. In some embodiments, the third doped region 617 is separated from the second doped regions 603 a′ 603 b′. In some embodiments, the third doped region 617′ is between the second doped regions 603 a′, 603 b′. In some embodiments, a part of each of the second doped regions 603 a′, 603 b′ is formed in the absorption layer 602′, and the other part of the second doped regions 603 a′, 603 b′ is formed in the substrate 604′. The second doped regions 603 a′, 603 b are formed in both of the absorption layer 602′ and the substrate 604′. In some embodiments, each of the second doped regions 603 a′, 603 b′ covers a part of the interface between the substrate 604′ and the absorption layer 602′. In some embodiments, the second doped regions 603 a′, 603 b′ are of a second conductivity type different from the first conductivity type of the first doped regions 601 b′,603 b′. In some embodiments, the second doped regions 603 a′, 603 b′ include a second dopant and a dopant profile. The peak dopant concentrations of the second doped regions 603 a′, 603 b depend on the material of the control contact layers 606 b′, 606 a′ and the material of the absorption layer 602′ and the material of the substrate 604′, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, a concentration at the interface between the substrate 604′ and the absorption layer 602′ and covered by the second doped regions 603 a′, 603 b′ is between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped regions 603 a′, 603 b′ forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 606 b′, 606 a′. The second doped regions 603 a′, 603 b′ are for demodulating the carriers generated from the absorption layer 602′ based on the control of the control signals cs1, cs2. By forming the second doped regions 603 a′, 603 b′ covering the interface between the substrate 604′ and the absorption layer 602′, the photo-detecting apparatus 600 e can with a satisfied dark current and demodulation contrast at the same time. In some embodiments, the control contact layers 606 b′, 606 a′ can be entirely formed over the absorption layer 602′ or be entirely formed over the substrate 604′.

FIG. 6F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 f in FIG. 6F is similar to the photo-detecting apparatus 600 d in FIG. 6D, where the difference is described below. The control contact layers 606 a′, 606 b′ are entirely formed on the first surface 602 s′ of the absorption layer 602′.

FIG. 6G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 g in FIG. 6G is similar to the photo-detecting apparatus 600 f in FIG. 6F, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped region 603 b′ under the control contact layers 606 b′. The second doped regions 603 a′, 603 b′ in FIG. 6G are similar to the second doped regions mentioned before, such as second doped regions 603 a′, 603 b′ as described in FIG. 6E, except that the second doped regions 603 a′, 603 b′ in FIG. 6G are entirely formed in the absorption layer 602′.

FIG. 6H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 h in FIG. 6H is similar to the photo-detecting apparatus 600 d in FIG. 6D, where the difference is described below. In some embodiments, a distance d₄ between the readout contact layers 608 a′, 608 b′ is less than the width w₃ of the absorption layer 602′. In some embodiments, the photo-detecting apparatus 600 g is devoid of the fourth doped region 618 as described in FIG. 6D. In some embodiments, the photo-detecting apparatus 600 g further includes a blocking layer 619′ surrounding at least a portion of the absorption layer 602′. In some embodiments, the blocking layer 619′ is of a conductivity type the same as a conductivity type of the absorption layer 602. The blocking layer 619′ may block photo-generated charges in the absorption layer 602′ from reaching the substrate 604′, which increases the collection efficiency of photo-generated carriers of the photo-detecting apparatus 600 g. The blocking layer 619′ may also block photo-generated charges in the substrate 604′ from reaching the absorption layer 602′, which increases the speed of photo-generated carriers of the photo-detecting apparatus 600 g. The blocking layer 619′ may include a material the same as the material of the absorption layer 602′, the same as the material of the substrate 604′, a material as a combination of the material of the absorption layer 602′ and the material of the substrate 604′, or different from the material of the absorption layer 602′ and the material of the substrate 604′. In some embodiments, the shape of the blocking layer 619′ may be but not limited to a ring. In some embodiments, the blocking layer 619′ may reach the first surface 604 s of the substrate 604′.

Since the third doped region 617′ and blocking layer 619′ are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between third doped region 617′ and the blocking layer 619′, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 602′, for example, when the third doped region 617′ is of n-type and the blocking layer 619′ is of p-type, the electrons tend to move toward the third doped region 617′ and the holes tends to move toward the blocking layer 619′. The third doped region 617′ is operated to collect the electrons and serves as a preliminary collector. The blocking layer 619′ is operated to collect the holes. The electrons stored in the third doped region 617′ may be further moved to first doped region 601 b′ or the first doped region 601 a′ based on the control signals cs1, cs2. In some embodiments, the blocking layer 619′ may be biased by a bias voltage ca2 to discharge carriers not collected by the first doped regions 601 a′, 601 b′. Accordingly, the demodulation contrast of the photo-detecting apparatus 600 g is improved.

FIG. 6I illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 i in FIG. 6I is similar to the photo-detecting apparatus 600 g in FIG. 6G, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 633 a between the absorption layer 602′ and the control contact layer 606 a. The second switch may further include a second dielectric layer 633 b between the absorption layer 602′ and the control contact layer 606 b. The first dielectric layer 633 a prevents direct current conduction from the control contact layer 606 a′ to the absorption layer 602′, but allows an electric field to be established within the absorption layer 602′ in response to an application of a voltage to the control contact layer 606 a′. The second dielectric layer 633 b prevents direct current conduction from the control contact layer 606 b′ to the absorption layer 602′ but allows an electric field to be established within the absorption layer 602′ in response to an application of a voltage to the control contact layer 606 b′. The established electric field may attract or repel charge carriers within the absorption layer 602′.

FIG. 6J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 j in FIG. 6J is similar to the photo-detecting apparatus 600 i in FIG. 6I, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the first dielectric layer 633 a. The second switch further includes a second doped region 603 b′ under the second dielectric layer 633 b. The second doped regions 603 a′, 603 b′ are similar to the second doped regions mentioned before, such as the second doped regions 603 a′, 603 b′ as described in FIG. 6G.

FIG. 6K illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 k in FIG. 6K is similar to the photo-detecting apparatus 600 h in FIG. 6H, where the difference is described below. In some embodiments, the third doped region 617′ overlaps with a portion of the second doped region 603 a′ farther from the first doped region 601 a′ of the first switch. The third doped region 617′ also overlaps with a part of the second doped region 603 b′ farther from the first doped region 601 b′ of the second switch. In some embodiments, the part of the second doped region 603 a′ farther from the first doped region 601 a′ includes both of the third dopant and the second dopant, wherein the third dopant is different from the second dopant. Similarly, the part of the second doped region 603 b′ farther from the first doped region 601 b′ includes both of the third dopant and the second dopant.

FIG. 6L illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 l in FIG. 6L is similar to the photo-detecting apparatus 600 h in FIG. 6H, where the difference is described below. In some embodiments, the absorption layer 602′ of each pixel includes a hinder region 640. The hinder region 640 is between the second doped regions 603 a′, 603 b′ and is entirely overlapped with the third doped region 617′. In some embodiments, the hinder region 640 includes a dopant and is of a conductivity type different from the third conductivity type of the third doped region 617. In some embodiments, the hinder region 640 has a dopant and a dopant profile with a peak dopant concentration higher than the peak dopant concentration the third doped region 617. In some embodiments, the peak dopant concentration of the hinder region 640 is between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³.

The hinder region 640 can block the carriers to be collected from reaching the first surface 602 s′ of the absorption layer 602′. As a result, a surface leakage current between the two second doped regions 603 a′, 603 b′ of the photo-detecting apparatus 600 l is reduced.

FIG. 6M illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 m in FIG. 6M is similar to the photo-detecting apparatus 600 g in FIG. 6G, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 600 m further includes two counter-doped regions 651 a, 651 b in the absorption layer 602′. Each of the counter-doped regions 651 a, 651 b has a conductivity type different from the first conductivity type of the first doped regions 601 a′, 601 b′. For example, if the photo-detecting apparatus is configured to process the collected electrons for further application, the first doped regions 601 a′, 601 b′ are of n-type, the third doped region 617′ is of n-type, and the counter-doped regions 651 a, 651 b are of p-type. In some embodiments, the counter-doped regions 651 a, 651 b overlaps with a portion of the first doped region 601 a′, 601 b′ father from the third doped region 617′, and the other portions of the first doped regions 601 a′, 601 b′ are not overlapped with the counter-doped region 651 a, 651 b. In some embodiments, each of the first doped regions 601 a′, 601 b′ is entirely overlapped with the respective counter-doped region 651 a, 651 b.

In some embodiments, each of the counter-doped regions 651 a, 651 b includes a dopant and a dopant profile with a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁶ cm⁻³. In some embodiment, the peak dopant concentrations of the counter-doped region 651 a, 651 b are lower than the peak dopant concentrations of the first doped regions 601 b′, 601 a′. In some embodiments, the peak dopant concentration of the counter-doped region 651 a, 651 b is between 1×10¹⁶ cm⁻³ and 1×10¹⁹ cm⁻³. In some embodiments, the counter-doped regions 651 a, 651 b serve as dark-current reduction regions for reducing the dark current of the photo-detecting apparatus 600 m. Compared to a photo-detecting apparatus devoid of counter-doped region 651 a, 651 b, the photo-detecting apparatus including counter-doped region 651 a, 651 b overlapping at least a portion of the first doped regions 601 a′, 601 b′ has thinner depletion regions in the absorption layer 602, and thus the photo-detecting apparatus 600 m is with lower dark current.

FIG. 6N illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 n in FIG. 6N is similar to the photo-detecting apparatus 600 m in FIG. 6M, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 633 a between the absorption layer 602′ and the control contact layer 606 a′. The second switch may further include a second dielectric layer 633 b between the absorption layer 602′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

FIG. 6O illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 o in FIG. 6O is similar to the photo-detecting apparatus 600 m in FIG. 6M, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped region 603 b′ under the control contact layers 606 b′. The second doped regions 603 a′, 603 b′ are similar to the second doped regions mentioned before, such as the second doped regions 603 a′, 603 b′ as described in FIG. 6G.

FIG. 6P illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 p in FIG. 6P is similar to the photo-detecting apparatus 600 o in FIG. 6O, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 633 a between the absorption layer 602′ and the control contact layer 606 a′. The second switch may further include a second dielectric layer 633 b between the absorption layer 602′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

FIG. 6Q illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 q in FIG. 6Q is similar to the photo-detecting apparatus 600 m in FIG. 6M, where the difference is described below. In some embodiments, the entire first doped region 601 a′ is overlapped with the counter-doped region 651 a. In some embodiments, the counter-doped region 651 a is an asymmetric profile relative to the first doped region 601 a′ from the cross-sectional view of the photo-detecting device 600 q. The asymmetric profile of the counter-doped region 651 a is relative to the first doped region 601 a′. In some embodiments, the counter-doped region 651 a includes a first portion (not labeled) and a second portion (not labeled). The first portion is closer to the third doped region 617′ than the second portion is. The first portion has a first width W₅, and the second portion has a second width W₆ greater than the first width W₅. In some embodiments, the entire first doped region 601 b′ is overlapped with the counter-doped region 651 b. In some embodiments, the counter-doped region 651 b is an asymmetric profile relative to the first doped region 601 b′ from the cross-sectional view of the photo-detecting device 600 q. The asymmetric profile of the counter-doped region 651 b is relative to the first doped region 601 b′. In some embodiments, the counter-doped region 651 b includes a first portion (not labeled) and a second portion (not labeled). The first portion is closer to the third doped region 617′ than the second portion is. The first portion has a first width W₇, and the second portion has a second width W₈ greater than the first width W₇. In some embodiments, the first switch further includes a first dielectric layer 633 a between the absorption layer 602′ and the control contact layer 606 a′. In some embodiments, the second switch may further include a second dielectric layer 633 b between the absorption layer 602′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer and the second dielectric layer respectively as mentioned before, such as the first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

FIG. 6R illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 r in FIG. 6R is similar to the photo-detecting apparatus 600 q in FIG. 6Q, where the difference is described below. In some embodiments, the first switch further includes a second doped regions 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped regions 603 b′ under the control contact layers 606 b′. The second doped regions 603 a′, 603 b′ are similar to the second doped regions as mentioned before, such as the second doped regions 603 a′, 603 b′ as described in FIG. 6G. In some embodiments, the first switch further includes a first dielectric layer 633 a between the second doped regions 603 a′ and the control contact layer 606 a′. In some embodiments, the second switch may further include a second dielectric layer 633 b between the second doped regions 603 b′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer and the second dielectric layer mentioned before, such as the first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

FIG. 6S illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 s in FIG. 6S is similar to the photo-detecting apparatus 600 m in FIG. 6M, where the difference is described below. The pixel of the photo-detecting apparatus 600 s further includes two buried counter-doped regions 652 a, 652 b in the absorption layer 602′. In some embodiments, the buried counter-doped region regions 652 a, 652 b are separated from the first surface 602 s′ of the absorption layer 602′. In some embodiments, the buried counter-doped region 652 a is overlapped with the counter-doped region 651 a. In some embodiments, the buried counter-doped region 652 b is overlapped with the counter-doped region 651 b. The counter-doped region 651 a, 651 b and the buried counter-doped region regions 652 a, 652 b can be formed in different steps such as by different masks. In some embodiments, the buried counter-doped region 652 a extends from the counter-doped region 651 a toward the third doped region 617′. In some embodiments, the buried counter-doped region 652 b extends from the counter-doped region 651 b toward the third doped region 617′. In some embodiments, a part of the buried counter-doped region 652 a is between the control contact layer 606 a′ and the second surface 602 ss′. In some embodiments, a part of the buried counter-doped region 652 b is between the control contact layer 606 b′ and the second surface 602 ss′. In some embodiments, each of the buried counter-doped regions 652 a,652 b is of a conductivity type different from the first conductivity type of the first doped regions 601 b′,601 a′. In some embodiments, each of the buried counter-doped regions 652 a, 652 b includes a dopant and a dopant profile with a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁶ cm⁻³. In some embodiment, the peak dopant concentrations of the buried counter-doped regions 652 a, 652 b are lower than the peak dopant concentrations of the first doped regions 601 b′, 601 a′. In some embodiments, the peak dopant concentration of the buried counter-doped regions 652 a, 652 b is between 1×10¹⁶ cm⁻³ and 1×10¹⁹ cm⁻³. In some embodiments, a distance between the first surface 602 s′ of the absorption layer 602′ and a location of the buried counter-doped regions 652 a,652 b with the peak dopant concentration is not less than 50 nm. In some embodiments, the distance between the second surface 602 ss′ and the location of the buried counter-doped regions 652 a,652 b with the peak dopant concentration is not less than 50 nm, or not less than 300 nm. In some embodiments, a distance between the first surface 602 s′ of the absorption layer 602′ and a location of the buried counter-doped regions 652 a, 652 b having the peak dopant concentration is less than a distance between the second surface 602 ss′ and the location of the buried counter-doped regions 652 a, 652 b having the peak dopant concentration. In some embodiments, the distance between the first surface 602 s′ of the absorption layer 602′ and the buried counter-doped regions 652 a, 652 b having the peak dopant concentration of is between 50 nm and 400 nm. The dopant profile of each of the buried counter-doped regions 652 a, 652 b can be controlled by any suitable method, such as by implantation including providing multiple implant doses and energies. In some embodiments, the dopants of the buried counter-doped regions 652 a, 652 b and the dopants of the counter-doped regions 651 a, 651 b can be the same.

By the combination of the buried counter-doped regions 652 a, 652 b and the counter-doped regions 651 a, 651 b, the flow of the carriers in the absorption layer 602′ can be restricted in a certain path, and thus bulk dark current injection is reduced. For example, when the third doped region 617′ is of n-type and the blocking layer 619′ is of p-type, the electrons tend to move toward the third doped region 617′ and the holes tends to move toward the blocking layer 619′. The third doped region 617′ is operated to collect the electrons and serves as a preliminary collector. The electrons stored in the third doped region 617′ may be further moved to first doped region 601 b′ or the first doped region 601 a′ through the regions between the first surface 602 s′ of the absorption layer 602′ and the buried counter-doped regions 652 a, 652 b based on the control signals cs1, cs2. As a result, the dark current of the photo-detecting apparatus 600S is further reduced.

FIG. 6T illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 t in FIG. 6T is similar to the photo-detecting apparatus 600 s in FIG. 6S, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped region 603 b′ under the control contact layers 606 b′. The second doped regions 603 a′, 603 b′ are similar to the second doped regions mentioned before, such as the second doped regions 603 a′, 603 b′ as described in FIG. 6G. In some embodiments, the first switch further includes a first dielectric layer 633 a between the second doped regions 603 a′ and the control contact layer 606 a′. In some embodiments, the second switch may further include a second dielectric layer 633 b between the second doped regions 603 b′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer and the second dielectric layer mentioned before such as first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

FIG. 6U illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 u in FIG. 6U is similar to the photo-detecting apparatus 600 m in FIG. 6M, where the difference is described below. The pixel of the photo-detecting apparatus 600 u further includes shallow counter doped region 653 a, 653 b in the absorption layer 602′. In some embodiments, the shallow counter doped regions 653 a, 653 b are under the respective readout contact layers 608 a′, 608 b′ along the vertical direction D1. In some embodiments, the shallow counter doped region 653 a is overlapped with the counter-doped region 651 a and with the first doped regions 601 a′. In some embodiments, the shallow counter doped region 653 b is overlapped with the counter-doped region 651 b and with the first doped regions 601 b′. The counter-doped region 651 a, 651 b and the shallow counter doped region 653 a, 653 b can be formed in different steps such as by different masks. In some embodiments, each of the shallow counter doped regions 653 a, 653 b is of a conductivity type different from the first conductivity type of the first doped regions 601 b′, 601 a′. In some embodiments, each of the shallow counter doped region 653 a, 653 b includes a dopant and a dopant profile with a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁵ cm⁻³. In some embodiment, the peak dopant concentrations of the shallow counter doped region 653 a, 653 b are lower than the peak dopant concentrations of the first doped regions 601 b′, 601 a′. In some embodiments, the peak dopant concentration of the shallow counter doped region 653 a, 653 b is between 1×10¹⁵ cm⁻³ and 1×10¹⁸ cm⁻³ or between 1×10¹⁶ cm⁻³ and 5×10¹⁷ cm⁻³. In some embodiments, a distance between the first surface 602 s′ of the absorption layer 602′ and the shallow counter doped region 653 a, 653 b having the peak dopant concentration is not more than 50 nm. In some embodiments, the dopants of the shallow counter doped region 653 a, 653 b and the dopants of the counter-doped regions 651 a, 651 b can be the same. The shallow counter doped region 653 a, 653 b can passivate the surface defects present at the first surface 602 s′ of the absorption layer 602′. Besides, the shallow counter doped region 653 a, 653 b can further modify the depletion regions near the first surface 602 s′ of the absorption layer 602′. As a result, the dark current of the photo-detecting apparatus 600 u can be further reduced.

FIG. 6V illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 600 v in FIG. 6V is similar to the photo-detecting apparatus 600 u in FIG. 6U, where the difference is described below. In some embodiments, the first switch further includes a second doped region 603 a′ under the control contact layers 606 a′. The second switch further includes a second doped region 603 b′ under the control contact layers 606 b′. The second doped regions 603 a′, 603 b′ are similar to the second doped regions mentioned before, such as the second doped regions 603 a′, 603 b′ as described in FIG. 6G. In some embodiments, the first switch further includes a first dielectric layer 633 a between the second doped regions 603 a′ and the control contact layer 606 a′. In some embodiments, the second switch may further include a second dielectric layer 633 b between the second doped regions 603 b′ and the control contact layer 606 b′. The first dielectric layer 633 a and the second dielectric layer 633 b are similar to the first dielectric layer and the second dielectric layer mentioned before such as the first dielectric layer 633 a and the second dielectric layer 633 b as described in FIG. 6I.

In some embodiments, photo-detecting apparatus 600 g through 600 v may also include an isolation region (not shown) as described in FIG. 6D. In some embodiments, the conductivity type of the isolation region is different from the conductivity type of the blocking layer 619′. For example, if the conductivity type of the blocking layer 619′ is p-type, the conductivity type of the isolation region is n-type. The isolation region is separated from the blocking layer 619′.

FIG. 7A illustrates a cross-sectional view of a photo-detecting apparatus with surface depletion mode, according to some embodiments. The photo-detecting apparatus 700 a includes control metal lines 706 a, 706 b and readout metal lines 708 a, 708 b. The control metal lines 706 a, 706 b and the readout metal lines 708 a, 708 b are electrically coupled to the surface 702 s of the germanium-based light absorption material 702. The control metal lines 706 a, 706 b are respectively electrically coupled to the P-type regions 703 a, 703 b on the surface 702 s, and the readout metal line 708 a, 708 b are respectively electrically coupled to the N-type regions 701 a, 701 b on the surface 702 s. This embodiment forms an interlayer dielectric ILD on the surface 702 s and forms metals 721, 716 a, 716 b, 718 a, 718 b on the interlayer dielectric ILD. These metals 721, 716 a, 716 b, 718 a, 718 b can be biased to generate the depletion regions 721 d, 716 ad, 716 bd, 718 ad, 718 bd. The biases applied on the metals 721, 716 a, 716 b, 718 a, 718 b can be different or the same, or have some of the metals 721, 716 a, 716 b, 718 a, 718 b floating.

The depletion region 712 d can reduce the dark current between the P-type region 703 a and the P-type region 703 b. The depletion region 716 ad can reduce the dark current between the P-type region 703 a and the N-type region 701 a. The depletion region 716 bd can reduce the dark current between the P-type region 703 b and the N-type region 701 b. The depletion region 718 a can reduce the dark current between N-type region 701 a and another pixel (Not shown in FIG. 7A). The depletion region 718 b can reduce the dark current between N-type region 701 b and another pixel (Not shown in FIG. 7A). Therefore, by forming these surface depletion regions, the power consumption and the noise generation can be reduced.

As mentioned, the metals 721, 716 a, 716 b, 718 a, 718 b can be biased to generate the depletion regions 721 d, 716 ad, 716 bd, 718 ad, and 718 bd. In other applications, the metals 721, 716 a, 716 b, 718 a, 718 b can be biased to make the corresponding regions 721 d, 716 ad, 716 bd, 718 ad, 718 bd into accumulation or inversion, other than depletion.

In addition to the leakage reduction, the metals 721, 716 a, 716 b, 718 a, 718 b can reflect the residual optical signal IL into the germanium-based light absorption material 702 so as to be converted into electron-hole pairs accordingly. These metals 721, 716 a, 716 b, 718 a, 718 b serve like a mirror reflecting the light not being completely absorbed and converted by the germanium-based light absorption material 702 back to the germanium-based light absorption material 702 for absorption again. This would increase the overall absorption efficiency and therefore increase the system performance.

Furthermore, an alternative embodiment of the present disclosure is illustrated in FIG. 7B. Compared to FIG. 7A, this embodiment adds polarized dielectrics 721 e, 716 ae, 716 be, 718 ae, 718 be (e.g., HfO2) as shown in FIG. 7B. Since there are dipole existing in the polarized dielectrics 721 c, 716 ae, 716 be, 718 ae, 718 be, the depletion/accumulation/inversion regions 721 d, 716 ad, 716 bd, 718 ad, 718 bd may be generated without biasing or biasing the metals 721, 716 a, 716 b, 718 a, 718 b at a small bias.

FIG. 7C illustrates a planar view of the photo-detecting apparatus 700B. It is noted that the metals 721, 716 a, 716 b, 718 a, 718 b and the polarized dielectrics 721 c, 716 ae, 716 be, 718 ae, 718 be can be formed optionally. The device implementer can design a photo-detecting apparatus to include these elements or not based on different scenarios. Furthermore, in addition to adding the metals and polarized dielectrics in vertical direction as shown in FIG. 7C, there is also an alternative embodiment as shown in FIG. 7D, in which the metals 723 a, 723 b, and polarized dielectrics 725 a, 725 b are added in the horizontal direction.

FIG. 8A illustrates a cross-sectional view of a photo-detecting apparatus with surface ion implantation, according to some embodiments. The photo-detecting apparatus 800 a includes control metal lines 806 a, 806 b and readout metal lines 808 a, 808 b. The control metal lines 806 a, 806 b and the readout metal lines 808 a, 808 b are electrically coupled to the surface 802 s of the germanium-based light absorption material 802. The control metal lines 806 a, 806 b are respectively electrically coupled to the P-type regions 803 a, 803 b on the surface 802 s, and the readout metal lines 808 a, 808 b are respectively electrically coupled to the N-type regions 801 a, 801 b on the surface 802 s. In order to have a high surface resistance for a suppression of the surface leakage current, this embodiment utilizes neutral ion implantation as a surface treatment. As shown in this figure, the ion-processed regions 829, 831 a, 831 b, 833 a, 833 b are ion implanted (e.g., Si, Ge, C, H2), in which accelerated ions collide with the substance and make damage to the atomic periodicity or the crystalline structure in the area of implantation. The lattice damage such as atomic vacancies and interstitials breaks the periodic potential seen by electron envelope function, so the electrons/holes gain higher probability being scattered. This effect results into a lower mobility and hence a higher resistance.

FIG. 8B illustrates a planar view of a photo-detecting apparatus 800 a with surface ion implantation, according to some embodiments. As shown in the figure, the ion-processed regions 829, 831 a, 831 b, 833 a, 833 b are vertically formed between the doped areas 801 a, 801 b, 803 a, 803 b. In some implementations, the ion-processed region(s) can be formed in other place(s), so the present embodiment is a reference rather than a limit.

FIG. 9A illustrates a cross-sectional view of a photo-detecting apparatus with pixel to pixel isolation. The photo-detecting apparatus 900 a includes control metal lines 906 a, 906 b and readout metal lines 908 a, 908 b. The control metal lines 906 a, 906 b and the readout metal lines 908 a, 908 b are electrically coupled to the surface 902 s of the germanium-based light absorption material 902. The control metal lines 906 a, 906 b are respectively electrically coupled to the P-type regions 903 a, 903 b on the surface 902 s, and the readout metal line 908 a, 908 b are respectively electrically coupled to the N-type regions 901 a, 901 b on the surface 902 s. This embodiment includes an isolation region 924, which is formed as a ring surrounding the germanium-based light absorption material 902. In one implantation, the isolation region 924 is an N-type region. It depends on the types of the germanium-based light absorption material 902, the semiconductor substrate 904, and other factors, and the isolation region 924 may be implemented by a P-type region. With this isolation region 924, the photo-detecting apparatus 900 a has the effect of reducing the cross-talk signals and/or powers to neighbor devices.

FIG. 9B illustrates a planar view of the photo-detecting apparatus 900 a with pixel to pixel isolation. As shown in the figure, the isolation region 924 forms an entire ring. In other implementations, the isolation region 924 may be fragmented or discontinued.

FIG. 9C illustrates a cross-sectional view of a photo-detecting apparatus with pixel to pixel isolation. The photo-detecting apparatus 900 c forms an additional narrow and shallow isolation region 924 a inside isolation region 924. The doping concentration of the isolation region 924 and the doping concentration of the isolation region 924 a are different. This may be applied to inhibit the crosstalk through surface conduction paths.

FIG. 9D illustrates a cross-sectional view of a photo-detecting apparatus with pixel to pixel isolation. The photo-detecting apparatus 900 d forms an additional trench isolation region 924 b extending from the isolation region 924 a to the bottom surface of the semiconductor substrate 904. The trench isolation region 924 b may be an oxide trench, in which block the electrical path between the germanium-based light absorption material 902 and adjacent devices.

FIG. 9E illustrates a cross-sectional view of a photo-detecting apparatus with pixel to pixel isolation. The photo-detecting apparatus 900 e forms a trench isolation region 924 b extending from the top surface of the semiconductor substrate 904 to the bottom surface of the semiconductor substrate 904. The trench isolation region 924 a may be an oxide trench, which blocks the electrical path between the germanium-based light absorption material 902 and adjacent devices.

FIG. 10A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The embodiment of FIG. 10A includes and combines elements from the above embodiments. The photo-detecting apparatus 1000 a includes control metal lines 1006 a, 1006 b and readout metal lines 1008 a, 1008 b. The control metal lines 1006 a, 1006 b and the readout metal lines 1008 a, 1008 b are electrically coupled to the surface 1002 s of the germanium-based light absorption material 1002. The control metal lines 1006 a, 1006 b are respectively electrically coupled to the P-type regions 1003 a, 1003 b on the surface 1002 s. The readout metal lines 1008 a, 1008 b are respectively electrically coupled to the N-type regions 1001 a, 1001 b on the surface 1002 s. Similarly, the photo-detecting apparatus 1000 a is able to obtain a distance information by the optical signal IL. Specifically, when the optical signal IL is incoming to the absorbed region AR, it will be converted into electron-hole pairs and then separated by the electrical field generated between the P-type regions 1003 a, 1003 b. The electrons may move toward either N-type region 1001 a or N-type region 1001 b according to the control signals cs1, cs2. In some implementations, the control signals cs1 and cs2 are differential voltage signals. In some implementations, one of the control signals cs1 and cs2 is a constant voltage signal (e.g., 0.5 v) and the other control signal is a time-varying voltage signal (e.g., sinusoid signal, clock signal or pulse signal; in-between 0V and 1V). Due to a distance existing between the photo-detecting apparatus 1000 a and the target object (not shown in FIG. 10A), the optical signal IL has a phase delay with respect to the transmitted light transmitted by a transmitter (not shown in FIG. 10A). The transmitted light is modulated by a modulation signal and the electron-hole pairs are demodulated through the control metal lines 1006 a and 1006 b by another modulation signal. The electrons or the holes stored in the capacitor 1010 a and capacitor 1010 b will be varied according to the distance. Therefore, the photo-detecting apparatus 1000 a can obtain the distance information based on the voltage v1 on the capacitor 1010 a and the voltage v2 on the capacitor 1010 b. According to one embodiment, the distance information can be derived based on calculations with voltage v1 and voltage v2 as input variables. For one example, in a pulse time-of-flight configuration, voltage ratios related to voltage v1 and voltage v2 are used as input variables. In another example, in a continuous-wave time-of-flight configuration, in-phase and quadrature voltages related voltage v1 and voltage v2 are used as input variables.

In addition to detecting the distance, this photo-detecting apparatus 1000 a includes a different depth design for N-type regions 1001 a, 1001 b and P-type regions 1003 a, 1003 b, and also adds N-well 1011 a, 1011 b, which may reduce the leakage current between the P-type region 1003 a and the P-type region 1003 b. Second, the photo-detecting apparatus 1000 a includes a well-shape P-type region 1019 covering the germanium-based light absorption material 1002, which may collect and discharge the holes through the bias voltage ca2. Third, the photo-detecting apparatus 1000 a includes the passivation layer 1014 and inter-layer dielectric ILD to process the surface 1002 s to the defects existing on the surface 1002 s. Fourth, the photo-detecting apparatus 1000 a includes the metal 1021, which may or may not be biased to generate the accumulation, inversion, or depletion on the surface 1002 s. Moreover, the metal 1021 can be used as a mirror to reflect the residual optical signal IL back into the germanium-based light absorption material 1002 to be converted to electron-hole pairs. Fifth, the photo-detecting apparatus 1000 a adds silicides 1013 a, 1013 b, 1015 a, 1015 b to reduce the voltage drop. Sixth, the photo-detecting apparatus 1000 a can add the isolation region 1024, either implemented by doping materials or insulating oxides. The isolation region 1024 may be electrically coupled to a bias voltage ca3. In some implementations, the isolation region 1024 and the P-type region 1019 may be electrically coupled together by a metal layer, and the metal layer is left floated or being electrically coupled to a voltage source.

FIG. 10B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The structure of the photo-detecting apparatus 1000 b is similar to the photo-detecting apparatus 1000 a. The difference is that the control metal lines 1006 a, 1006 b in FIG. 10B are electrically coupled to the un-doped regions 1005 a, 1005 b.

Furthermore, although the above-mentioned embodiments use a germanium-based light absorption material 1002 to absorb the optical signal IL, one embodiment without germanium-based light absorption material 1002 may be implemented. As shown in FIG. 10C, photo-detecting apparatus 1000 c can use the semiconductor substrate 1004 as the light absorption material. In some implementations, the semiconductor substrate 1004 can be silicon, silicon-germanium, germanium, or III-V compounds. Besides, P-type regions 1003 a, 1003 b and N-wells 1011 a, 1011 b may be added on the surface 1002 s of the semiconductor substrate 1004, as the embodiment illustrated in FIG. 10D.

The photo-detecting apparatuses 1000 a, 1000 b, 1000 c and 1000 d are illustrated to show the possible combinations from embodiments (FIG. 1A to FIG. 9E) disclosed above. It is understood that the device implementer can arbitrarily combine two or more above embodiments to implement other photo-detecting apparatus(s) and numerous combinations may be implemented.

It is noted that the doping concentrations for the doped regions shown in the embodiments can be properly designed. Take the embodiment of FIG. 10A as an example, the doping concentrations of the N-type regions 1001 a, 1001 b and the doping concentrations of the P-type regions 1003 a, 1003 b could be different. In one implementation, the P-type regions 1003 a, 1003 b are lightly doped and N-type regions 1001 a, 1001 b are highly doped. In general, the doping concentration for the lightly doping may range from 10¹⁶/cm³ or less to 10¹⁸/cm³, and the doping concentration for the highly doping may range from 10¹⁸/cm³ to 10²⁰/cm³ or more. Through the doping concentration adjustment, the Schottky contacts can be formed between the control metal lines 1006 a, 1006 b and the P-type regions 1003 a, 1003 b respectively; and the Ohmic contacts can be formed between the readout metal lines 1008 a, 1008 b and N-type regions 1001 a, 1001 b respectively. In this scenario, the resistances between control metal lines 1006 a, 1006 b and the P-type regions 1003 a, 1003 b are higher than the resistances between readout metal lines 1008 a, 1008 b and the N-type regions 1001 a, 1001 b.

On the other hands, the doping type for those doped regions can also be implemented in different ways. Take the embodiment of FIG. 10A as an example, The P-type regions 1003 a, 1003 b can be replaced by N-type if the regions 1003 a, 1003 b are doped with N-type dopants. Similarly, the N-type regions 1001 a, 1001 b can be replaced by P-type if the regions 1001 a, 1001 b are doped with P-type dopants. Therefore, it is possible to implement an embodiment that the doped regions 1001 a, 1001 b, 1003 a and 1003 b all are doped with same type dopants.

Please refer to FIG. 11A, which illustrates a planar view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1100 a includes the layout positions for control metal lines 1106 a, 1106 b, readout metal lines 1108 a, 1108 b, N-type regions 1001 a, 1001 b and P-type regions 1003 a, 1003 b on the germanium-based light absorption material 1102. In this embodiment, the control metal lines 1106 a, 1106 b are positioned on the axis X axis, however, readout metal lines 1108 a, 1108 b are not positioned on the axis X axis. In this embodiment, the four terminals are not on the same axis, which may reduce the area of the photo-detecting apparatus 1100 a. The geometric relations between each element are shown in FIG. 11A.

FIG. 11B illustrates a planar view of a photo-detecting apparatus, according to some embodiments. Compared to FIG. 11A, the control metal lines 1106 a, 1106 b are not positioned on the axis X axis, but respectively aligned with readout metal lines 1108 a, 1108 b in the direction perpendicular to the axis X axis. Similarly, the geometric relations between each element are shown in FIG. 11B.

FIG. 11C illustrates a planar view of a photo-detecting apparatus, according to some embodiments. The control metal lines 1106 a, 1106 b are formed above the absorbed region AR and opposing each other in a diagonal direction in the optical window WD. The readout metal lines 1108 a, 1108 b are formed on the axis X axis.

FIG. 11D illustrates a planar view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus in FIG. 11D is similar to that in FIG. 11C, but the germanium-based light absorption material 1102 is rotated so that the axis X axis is in a diagonal direction in the germanium-based light absorption material 1102. It may also reduce the overall area of the photo-detecting apparatus.

FIG. 11E illustrates a planar view of a photo-detecting apparatus, according to some embodiments. The difference between this embodiment and previous embodiments is the optical window WD can be designed as an Octagon. It can also be designed as other shapes (e.g. circle and hexagon etc.).

FIG. 11A-FIG. 11D illustrates some embodiments by adjusting the layout positions for control metal lines 1106 a, 1106 b, readout metal lines 1108 a, 1108 b, N-type regions 1001 a, 1001 b, and P-type regions 1003 a, 1003 b. The implementer can also design different geometric relations for these elements to reduce or minimize the chip area. These alternative embodiments are illustrated as a reference, not a limit.

The photo-detecting apparatuses described above use a single photodetector as an embodiment, which is for single-pixel applications. The photo-detecting apparatuses described below are the embodiments for multiple-pixel applications (e.g., image pixel array or image sensor).

In some implementations, the photo-detecting apparatus can be designed to receive the same or different optical signals, e.g., with the same or different wavelengths, with the same or multiple modulations, or being operated at different time frames.

Please refer to FIG. 12A. The photo-detecting apparatus 1200 a comprises a pixel array, which includes four pixels 12021, 12022, 12023, 12024 as an example. Each pixel is a photodetector in accordance with the embodiments described herein. In one embodiment, optical signal IL that contains optical wavelength λ₁ is received by the pixels 12021, 12024 in this array, and optical signal IL that contains optical wavelength λ₂ is received by pixels 12022, 12023 in this array. In an alternative embodiment, there is only one optical wavelength λ but having multiple modulation frequencies f_(mod1) and f_(mod2) (or more). For example, the pixels 12021, 12024 are applied with modulation frequency f_(mod1) to demodulate this frequency component in the optical signal IL, and the pixels 12022, 12023 are applied with modulation frequency f_(mod2) to demodulate this frequency component in the optical signal IL. In an alternative embodiment, similarly, there is only one optical wavelength λ but having multiple modulation frequencies f_(mod1) and f_(mod2) (or more). However, at time t₁, the pixels in the array are driven by modulation frequency f_(mod1) to demodulate this frequency component in the optical signal, while at another time t₂, the pixels in the array are driven by modulation frequency f_(mod2) to demodulate this frequency component in the optical signal IL, and thus the pixel array 1200 a is operated under time multiplexing mode.

In an alternative embodiment, optical wavelengths λ₁ and λ₂ are respectively modulated by f_(mod1) and f_(mod2), and then collected by pixel array 1200 a. At time t₁, the pixel array 1200 a is operated at f_(mod1) to demodulate the optical signal in λ₁; while at time t₂, the pixel array 1200 a is operated at f_(mod2) to demodulate the optical signal in λ₂. In an alternative embodiment, an optical signal IL with optical wavelength λ₁ and λ₂ is modulated by f_(mod1) and f_(mod2), respectively, and the pixels 12021, 12024 are driven by f_(mod1) while the pixels 12022, 12023 are driven by f_(mod2) to demodulate the incoming modulated optical signal IL simultaneously. Those of skills in the art will readily recognize that other combinations of optical wavelength, modulation scheme and time division may be implemented.

Please refer to FIG. 12B. The photo-detecting apparatus 1200 b includes four pixels 12021, 12022, 12023, 12024. Each pixel is a photodetector and may use the embodiments disclosed above. In addition to the layout shown in FIG. 12A, the pixels 12021, 12022, 12023, 12024 can be arranged in a staggered layout as shown in FIG. 12B, in which the width and length of each pixel are placed in directions perpendicular to the width and length of the adjacent pixels.

FIG. 13A illustrates a block diagram of a photo-detecting apparatus 1300 a using modulation schemes with phase changes, according to some embodiments. The photo-detecting apparatus 1300 a is an indirect time-of-flight based depth image sensor capable of detecting a distance information with the targeted object 1310. The photo-detecting apparatus 1300 a includes a pixel array 1302, laser diode driver 1304, laser diode 1306, and clock driving circuit 1308 including clock drivers 13081, 13082. The pixel array 1302 includes a plurality of photodetectors in accordance with the embodiments disclosed herein. In general, the sensor chip generates and sends out the clock signals for 1) modulating the transmitted optical signal by the laser diode driver 1304 and 2) demodulating the received/absorbed optical signal by the pixel array 1302. To obtain the depth information, all photodetectors in an entire pixel array are demodulated by referencing the same clock, which changes to possible four quadrature phases, e.g., 0°, 90°, 180° and 270°, in a temporal sequence and there is no phase change at the transmitter side. However, in this embodiment, the 4-quadrature phase changes are implemented at the transmitter side, and there is no phase change at the receiving side, as explained in the following.

Please refer to FIG. 13B, which depicts a timing diagram of the clock signals CLK1, CLK2 generated by clock drivers 13081, 13082, respectively. The clock signal CLK1 is a modulation signal with 4-quadrature phase changes, e.g., 0°, 90°, 180° and 270°, and clock signal CLK2 is a demodulation signal without phase change. Specifically, the clock signal CLK1 drives the laser diode diver 1304 so that the laser diode 1306 can generate the modulated transmitted light TL. The clock signal CLK2 and its reversed signal CLK2′ (not shown in FIG. 13B) are used as the control signal cs1 and control signal cs2 (shown in the above embodiments), respectively, for demodulation. In other words, the control signal cs1 and control signal cs2 in this embodiment are differential signals. This embodiment may avoid the possible temporal coherence inherent in an image sensor due to parasitic resistance-capacitance induced memory effects.

Please refer to FIG. 13C and FIG. 13D. Compared to the FIG. 13A, the photo-detecting apparatus 1300 c uses two demodulation schemes at the receiving side. The pixel array 1302 includes two portions, the first pixel array 1302 a and the second pixel array 1302 b. The first demodulation scheme applied to the first pixel array 1302 a and the second demodulation scheme applied to the second pixel array 1302 b are different in temporal sequence. For example, the first pixel array 1302 a is applied with the first demodulation scheme, in which the phase changes in temporal sequence are 0°, 90°, 180° and 270°. The second pixel array 1302 a is applied with the second demodulation scheme, in which the phase changes in temporal sequence are 90°, 180°, 270° and 0°. The net effect is the phase changes in the first pixel array 1302 a are in phase quadrature to the phase changes in the second pixel array 1302 b, while there are no phase changes at the transmitting side. This operation may reduce the max instantaneous current drawn from the power supply if the demodulation waveform is not an ideal square wave.

Please refer to FIG. 13E, which shows a modulation scheme using the photo-detecting apparatus 1300 c. Compared to FIG. 13D, this embodiment applies phase changes to the transmitting side, but does not apply phase changes to the two different pixel arrays 1302 a, 1302 b at the receiving side, except setting two different constant phases to the two different pixel arrays 1302 a, 1302 b, and the two different constant phases are in phase quadrature to each other. For example, the modulation signal at the transmitting side is the clock signal CLK1, in which the phase changes in temporal sequence are 0°, 90°, 180°, and 270°. The demodulation signals at the receiving side are clock signals CLK2, CLK3. The clock signal CLK2 is used to demodulate the incident optical signal IL absorbed by pixel array 1302 a, which has a constant phase of 0°. The clock signal CLK3 is used to demodulate the incident optical signal IL absorbed by pixel array 1302 b, which has a constant phase of 90°.

Although the embodiments illustrated in FIG. 13A-13E use clock signals with a 50% duty cycle as the modulation and demodulation signals, in other possible implementations, the duty cycle can be different (e.g. 30% duty cycle). In some implementations, sinusoidal wave is used as the modulation and demodulation signals instead of square wave.

FIG. 14 illustrates a process for using the photo-detecting apparatus using modulation schemes with phase changes, according to some embodiments. Other entities perform some or all of the steps of the process in other embodiments. Likewise, embodiments may include different and/or additional steps, or perform the steps in different orders.

In the embodiment of FIG. 14, the photo-detecting method comprises step 1401: transmitting an optical signal modulated by a first modulation signal, wherein the optical signal is modulated by the first modulation signal with one or multiple predetermined phase(s) for multiple time frames; step 1402: receiving the reflected optical signal by a photodetector; step 1403: demodulating the reflected optical signal by one or multiple demodulation signal(s), wherein the one or multiple demodulation signal(s) is/are the signal(s) with one or multiple predetermined phase(s) for multiple time frames; and step 1404: outputting at least one voltage signal on a capacitor. In this method, the photodetector may use the embodiments mentioned in the present disclosure or its variants.

FIG. 15A illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 a includes a substrate 1504. The photo-detecting apparatus 1500 a further includes a pixel (not labeled) including an absorption layer 1502 supported by a substrate 1504. The pixel further includes an absorbed region AR in the absorption layer 1502 and defined by a light shield (not shown). The absorbed region AR is a virtual area receiving the optical signal incoming through the light shield. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 1502. The first switch includes a control contact layer 1506 a and a readout contact layer 1508 a. The second switch includes a control contact layer 1506 b and a readout contact layer 1508 b. In some embodiments, the readout contact layers 1508 a, 1508 b, the control contact layers 1506 a, 1506 b are formed over a first surface of the absorption layer 1502. In some embodiments, the readout contact layers 1508 a, 1508 b, and the control contact layers 1506 a, 1506 b are formed at the same side of the absorbed region AR. In some embodiments, a distance between the readout contact layers 1508 a, 1508 b along a Y direction Y1 is greater than a distance between the control contact layers 1506 a, 1506 b along a Y direction Y1 from the top view of the photo-detecting apparatus 1500 a. In some embodiments, the control contact layers 1506 a, 1506 b are closer to the absorbed region AR than the readout contact layers 1508 a, 1508 b is along a direction substantially perpendicular to the Y direction Y1 from the top view of the photo-detecting apparatus 1500 a.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 1508 a. The second readout circuit is electrically coupled to the readout contact layer 1508 b.

The pixel may also include control signals (not shown) controlling the control contact layers 1506 a, 1506 b, as described in the embodiments mentioned before.

In some embodiments, the pixel further includes a guiding region 1517 formed in the absorption layer 1502 and between the first switch and the second switch. In some embodiments, the guiding region 1517 is between the portions of the absorption layer 1502 right under the control contact layers 1506 a, 1506 b. In some embodiments, a part of the guiding region 1517 is in the absorbed region AR. That is, the guiding region 1517 is overlapped with the absorbed region AR along a direction substantially perpendicular to the first surface of the absorption layer 1502. In some embodiments, the guiding region 1517 is of a conductivity type. In some embodiments, if the photo-detecting apparatus is configured to collects electrons, the guiding region 1517 is of n-type. In some embodiments, if the photo-detecting apparatus is configured to collects holes, the guiding region 1517 is of p-type. In some embodiments, the guiding region 1517 is not coupled to any external control and thus is floated.

In some embodiments, the guiding region 1517 includes a dopant and has a dopant profile with a peak dopant concentration not less than 1×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the guiding region 1517 is between 1×10¹⁵ cm⁻³ and 1×10¹⁷ cm⁻³.

The guiding region 1517 is for facilitating the carriers flowing from the absorbed region AR toward the direction where the first switch and the second switch disposed first, and then the carriers are demodulated through the control contact layers 1506 a, 1506 b based on the control of the two control signals (not shown).

The photo-detecting apparatus 1500 a includes multiple repeating pixels. The photo-detecting apparatus 1500 a includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the photo-detecting apparatus 1500 a further includes a blocking layer 1519 surrounding at least a portion of the absorption layer 1502. The blocking layer 1519 is of a conductivity type. In some embodiments, the blocking layer 1519 is of a conductivity type the same as a conductivity type of the absorption layer 1502. The blocking layer 1519 may block photo-generated charges in the absorption layer 1502 from reaching the substrate 1504, which increases the collection efficiency of photo-generated carriers of the photo-detecting apparatus 1500 a. The blocking layer 1519 may also block photo-generated charges in the substrate 1504 from reaching the absorption layer 1502′, which increases the speed of photo-generated carriers of the photo-detecting apparatus 1500 a. The blocking layer 1519 may include a material the same as the material of the absorption layer 1502, the same as the material of the substrate 1504, a material as a combination of the material of the absorption region 1502 and the material of the substrate 1504, or different from the material of the absorption layer 1502 and the material of the substrate 1504. In some embodiments, the shape of the blocking layer 1519 may be but not limited to a ring. In some embodiments, the blocking layer 1519 includes a dopant and has a dopant profile with a peak dopant concentration ranging from 10¹⁵ cm⁻³ to 10²⁰ cm⁻³. The blocking layer 1519 may reduce the cross talk between two adjacent pixels.

FIG. 15B illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 b in FIG. 15B is similar to the photo-detecting apparatus 1500 a in FIG. 15A, where the difference is described below. In some embodiments, the distance between the readout contact layers 1508 a, 1508 b along a Y direction Y1 can be substantially the same as the distance between the control contact layers 1506 a, 1506 b along a Y direction Y1. In some embodiments, the control contact layer 1506 a is between the absorbed region AR and the readout contact layer 1508 a. In some embodiments, the control contact layer 1506 b is between the absorbed region AR and the readout contact layer 1508 b. In some embodiments, the guiding region 1517 may be adjacent to the absorbed region AR and not overlapped with the absorbed region AR.

FIG. 15C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, FIG. 15C illustrates a cross-sectional view along an A-A′ line in FIG. 15A or in FIG. 15B. In some embodiments, the cross-sectional view shown in FIG. 15C may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus. In some embodiments, the first switch further includes a first doped region 1501 a under the readout contact layers 1508 a. The second switch further includes a first doped region 1501 b under the readout contact layers 1508 b. In some embodiments, the first doped regions 1501 a, 1501 b are of a first conductivity type. In some embodiments, the first doped regions 1501 a, 1501 b include a first dopant. The peak dopant concentrations of the first doped regions 1501 a, 1501 b depend on the material of the readout contact layers 1508 a, 1508 b and the material of the absorption layer 1502, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The first doped regions 1501 a, 1501 b are for collecting the carriers generated from the absorption layer 1502, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals (not shown).

In some embodiments, the blocking layer 1519 is of a conductivity type different from the first conductivity type of each of the first doped regions 1501 b, 1501 a. In some embodiments, the peak dopant concentration of the guiding region 1517 is lower than the peak dopant concentration of the first doped regions 1501 a, 1501 b. In some embodiments, the photo-detecting apparatus 1500 c further includes a conductive layer (not shown) electrically coupled to the blocking layer 1619. In some embodiments, the blocking layer 1519 may be biased by a bias voltage through the conductive layer to discharge carriers not collected by the first doped regions 1501 a, 1501 b.

In some embodiments, the first switch further includes a second doped region 1503 a under the control contact layer 1506 a. The second switch further includes a second doped region 1503 b under the control contact layer 1506 b. In some embodiments, the second doped regions 1503 a, 1503 b are of a second conductivity type different from the first conductivity type of the first doped regions 1501 b, 1501 a. In some embodiments, the second doped regions 1503 a, 1503 b include a second dopant. The peak dopant concentrations of the second doped regions 1503 a, 1503 b depend on the material of the control contact layers 1506 b, 1506 a and the material of the absorption layer 1502, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped regions 1503 a, 1503 b forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 1506 b, 1506 a. The second doped regions 1503 a, 1503 b are for demodulating the carriers generated from the absorption layer 1502 based on the control of the control signals (not shown). In some embodiments, the guiding region 1517 is between the second doped regions 1503 a, 1503 b.

In some embodiments, each of the second doped regions 1503 a, 1503 b has a depth greater than a depth of each of the first doped regions 1501 a, 1501 b. The depth is measured from the first surface 1502′ of the absorption layer 1502 to a position where the dopant reaches a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the guiding region 1517 has a depth not more than the depth of each of the second doped regions 1503 a, 1503 b.

In some embodiments, the guiding region 1517 may be floated. In some embodiments, the photo-detecting apparatus 1500 c may further include a conductive layer (not shown) electrically connected to the guiding region 1517. In some embodiments, the guiding region 1517 may be biased through the conductive layer by a bias voltage. In some embodiments, the guiding region 1517 and the blocking layer 1519 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between the guiding region 1517 and the blocking layer 1519, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 1502. The term “vertical” is a direction substantially perpendicular to the first surface of the absorption layer 1502.

FIG. 15D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, the cross-sectional view shown in FIG. 15D may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus. The photo-detecting apparatus 1500 d in FIG. 15D is similar to the photo-detecting apparatus 1500 c in FIG. 15C, where the difference is described below. In some embodiments, the photo-detecting apparatus further 1500 d includes two counter-doped regions 1551 a, 1551 b. In some embodiments, the counter-doped regions 1551 a, 1551 b are formed in the absorption layer 1502. In some embodiments, the counter-doped region 1551 a overlaps with at least a portion of the first doped region 1501 a. The counter-doped region 1551 b overlaps with at least a portion of the first doped region 1501 b. In some embodiments, the counter-doped regions 1551 a, 1551 b overlaps with a portion of the first doped region 1501 a, 1501 b father from the control contact layers 1506 a, 1506 b, and the other portions of the first doped regions 1501 a, 1501 b are not overlapped with the counter-doped region 1551 a, 1551 b. In some embodiments, each of the first doped regions 1501 a, 1501 b is entirely overlapped with respective counter-doped region 1551 a, 1551 b.

Each of the counter-doped regions 1551 a, 1551 b has a conductivity type different from the first conductivity type of the first doped region 1501 a, 1501 b. For example, if the first doped regions 1501 a, 1501 b are of n-type, the counter-doped regions 1551 a, 1551 b are of p-type. In some embodiments, each of the counter-doped regions 1551 a, 1551 b includes a dopant having a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁶ cm⁻³. In some embodiment, the peak dopant concentrations of the counter-doped regions 1551 a, 1551 b are lower than the peak dopant concentrations of the first doped regions 1501 b, 1501 a. In some embodiments, the peak dopant concentration of each of the counter-doped regions 1551 a, 1551 b is between 1×10¹⁶ cm⁻³ and 1×10¹⁹ cm⁻³. In some embodiments, the counter-doped regions 1551 a, 1551 b serve as dark-current reduction regions for reducing the dark current of the photo-detecting apparatus 1500 d. Compared to a photo-detecting apparatus devoid of counter-doped region 1551 a, 1551 b, the photo-detecting apparatus 1500 d including counter-doped region 1551 a, 1551 b overlapped with at least a portion of the first doped region 1501 a, 1501 b has thinner depletion regions in the absorption layer 1502, and thus the photo-detecting apparatus 1500 d is with lower dark current.

In some embodiments, the counter-doped regions 1551 a, 1551 b may reduce the coupling between the two first doped regions 1501 a, 1501 b.

In some embodiments, the photo-detecting apparatus 1500 d may further include a conductive layer 1521 electrically connected to the blocking layer 1519. The blocking layer 1519 may be biased through the conductive layer 1521 by a bias voltage to discharge carriers not collected by the first doped regions 1501 a, 1501 b. In some embodiments, the blocking layer 1519 may be biased and thus provides a vertical electric field between the blocking layer 1519 and the guiding region 1517, which may assist in separating the electron-hole pairs generated in the absorbed region AR. In some embodiments, the photo-detecting apparatus 1500 d may further include another conductive layer (not shown) electrically connected to the guiding region 1517 to bias the guiding region 1517, which further enhances the vertical electric field between the blocking layer 1519 and the guiding region 1517.

FIG. 15E illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 e in FIG. 15E is similar to the photo-detecting apparatus in FIG. 15A, where the difference is described below. The photo-detecting apparatus 1500 e is devoid of a blocking layer 1519. The readout contact layers 1508 a, 1508 b, the control contact layers 1506 a, 1506 b are formed over a first surface of the substrate 1504. The guiding region 1517 is formed in both of the absorption layer 1502 and the substrate 1504. In other words, a portion of the guiding region 1517 is in the absorption layer 1502, the other portion of the guiding region 1517 is in the substrate 1504. In some embodiments, the guiding region 1517 covers a part of the interface between the substrate 1504 and the absorption layer 1502. In some embodiments, the photo-detecting apparatus 1500 e further includes an isolation region 1524 formed in the substrate 1504 and surrounding the absorption layer 1502, the readout contact layers 1508 a, 1508 b, and the control contact layers 1506 a, 1506 b from the top view of the photo-detecting apparatus 1500 e. The isolation region 1524 is separated from the absorption layer 1502. In some embodiments, the isolation region 1524 is a trench filled with a dielectric material or an insulating material to serve as a region of high electrical resistance between the two adjacent pixels, impeding a flow of current across the isolation region 1524 and improving electrical isolation between the adjacent pixels. The dielectric material or an insulating material may include, but is not limited to oxide material including SiO₂ or nitride material including Si₃N₄ or silicon material including amorphous-Si, poly-Si, monocrystalline-Si or epitaxial-Si. In some embodiments, from a cross-sectional; view of the photo-detecting apparatus 1500 e, the isolation region 1524 extends from a first surface (not labeled) of the substrate 1504′ and extends into a predetermined depth from the first surface. In some embodiments, the isolation region 1524 extends from a second surface (not shown) of the substrate 1504 and extends into a predetermined depth from the second surface. In some embodiments, the isolation region 1524 penetrates though the substrate 1504 from the first surface to the second surface.

In some embodiments, the isolation region 1524 is a doped region having a conductivity type. The doping of the isolation region 1524 may create a bandgap offset-induced potential energy barrier that impedes a flow of current across the isolation region 1524 and improving electrical isolation between the adjacent pixels of the photo-detecting apparatus 1500 e. In some embodiments, the isolation region 1524 includes a semiconductor material that is different from the material of the substrate 1504. An interface between two different semiconductor materials formed between the substrate 1504 and the isolation region 1524 may create a bandgap offset-induced energy barrier that impedes a flow of current across the isolation region 1524 and improving electrical isolation between the adjacent pixels of the photo-detecting apparatus 1500 e. In some embodiments, the shape of the isolation region 1524 may be a ring. In some embodiments, the isolation region 1524 may include two discrete regions disposed at the two opposite sides of the absorption layer 1502′.

FIG. 15F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, FIG. 15F illustrates a cross-sectional view along an A-A′ line in FIG. 15E. In some embodiments, the cross-sectional view shown in FIG. 15F may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus. In some embodiments, the first switch of the photo-detecting apparatus 1500 f further includes a first doped region 1501 a, which is similar to the first doped region as mentioned before, such as the first doped region 1501 a as described in FIG. 15C. In some embodiments, the second switch further includes a first doped region 1501 b, which is similar to the first doped region as mentioned before, such as first doped region 1501 b as described in FIG. 15C. In some embodiments, the first switch further includes a second doped region 1503 a, which is similar to the second doped region as mentioned before, such as the second doped region 1503 a as described in FIG. 15C. In some embodiments, the second switch includes a second doped region 1503 b, which is similar to the second doped region as mentioned before, such as the second doped region 1503 b as described in FIG. 15C. The guiding region 1517 is between the second doped regions 1503 a, 1503 b. In some embodiments, the conductivity type of the isolation region 1524 can be different from or the same as the first conductivity type of the first doped regions 1501 a, 1501 b.

FIG. 15G illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 g in FIG. 15G is similar to the photo-detecting apparatus 1500 e in FIG. 15E, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus further includes a discharging region 1518 formed in the absorption layer 1502. In some embodiments, the discharging region 1518 is disposed at a side of the absorbed region AR opposite to the side of the absorbed region AR where the first switch and the second switch are disposed. In some embodiments, the absorbed region AR is between the discharging region 1518 and the control contact layer 1506 a or the control contact layer 1506 b.

The discharging region 1518 is of a conductivity type different from conductivity type of the guiding region 1517. In some embodiments, the discharging region 1518 includes a dopant and has a dopant profile with a peak dopant concentration ranging from 1×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. The discharging region 1518 is for discharging the carriers not collected by the first doped regions 1501 a, 1501 b during the operation of the photo-detecting apparatus 1500 g. Therefore, the photo-detecting apparatus 1500 g is with improved reliability and quantum efficiency. In some embodiments, the pixel of the photo-detecting apparatus 1500 g further includes a conductive layer 1541 electrically coupled to the discharging region 1518 and disposed over the absorption layer 1502 for biasing the discharging region 1518. For example, if the photo-detecting apparatus 1500 g is configured to collect electrons, the holes may be discharged through the discharging region 1518 and the conductive layer 1541.

FIG. 15H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, FIG. 15H illustrates a cross-sectional view along a B-B′ line in FIG. 15G. In some embodiments, the cross-sectional view shown in FIG. 15H may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus.

FIG. 15I illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 i in FIG. 15I is similar to the photo-detecting apparatus 1500 a in FIG. 15A, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1500 i further includes a discharging region 1518, which is similar to the discharging region 1518 described in FIG. 15G. Where the difference is described below. The discharging region 1518 is formed in both of the absorption layer 1502 and the substrate 1504. In other words, a portion of the discharging region 1518 is in the absorption layer 1502, the other portion of the discharging region 1518 is in the substrate 1504. The pixel of the photo-detecting apparatus 1500 i further includes a conductive layer 1541 electrically coupled to the discharging region 1518 for biasing the discharging region 1518, as described in FIG. 15G. The conductive layer 1541 is disposed over the substrate 1504 and overlapped with the discharging region 1518.

FIG. 15J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, FIG. 15J illustrates a cross-sectional view along a B-B′ line in FIG. 15I. In some embodiments, the cross-sectional view shown in FIG. 15J may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus.

FIG. 15K illustrates a top view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1500 k in FIG. 15K is similar to the photo-detecting apparatus 1500 e in FIG. 15E, where the difference is described below. In some embodiments, the control contact layers 1506 a, 1506 b are over a first surface of the absorption layer 1502, which may increase the lateral electric field between the portions in the absorption layer 1502 right under the control contact layers 1506 a, 1506 b. In some embodiments, the pixel of the photo-detecting apparatus 1500 k may further include a discharging region 1518 as described in FIG. 15G or in FIG. 15I. In some embodiments, the photo-detecting apparatus 1500 k may further include a conductive layer 1541 as described in FIG. 15G or in FIG. 15I.

FIG. 15L illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. In some embodiments, FIG. 15L illustrates a cross-sectional view along a A-A′ line in FIG. 15K. In some embodiments, the cross-sectional view shown in FIG. 15L may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus. In some embodiments, the first switch further includes a first doped region 1501 a, which is similar to the first doped region as mentioned before, such as the first doped regions 1501 a as described in FIG. 15C. In some embodiments, the second switch further includes a first doped region 1501 b, which is similar to the first doped region as mentioned before, such as the first doped regions 1501 b as described in FIG. 15C. In some embodiments, the first switch further includes a second doped region 1503 a, which is similar to the second doped region as mentioned before, such as the second doped regions 1503 a as described in FIG. 15C. In some embodiments, the second switch includes a second doped region 1503 b, which is similar to the second doped region as mentioned before, such as the second doped regions 1503 b as described in FIG. 15C. The guiding region 1517 is between the second doped regions 1503 a, 1503 b.

FIG. 16A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 a includes a substrate 1604. The photo-detecting apparatus 1600 a further includes a pixel including an absorption layer 1602 supported by the substrate 1604. The pixel includes an absorbed region AR similar to the absorbed region AR mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 1602. The first switch includes a control contact layer 1606 a and a readout contact layer 1608 a. The second switch includes a control contact layer 1606 b and a readout contact layer 1608 b. In some embodiments, the readout contact layers 1608 a, 1608 b and the control contact layer 1606 a, 1606 b are formed over a first surface 1602 s of the absorption layer 1602. In some embodiments, a width of the absorbed region AR is less than a distance between the readout contact layers 1608 a, 1608 b. In some embodiments, the readout contact layers 1608 a, 1608 b are disposed at two opposite sides of the absorbed region AR.

The photo-detecting apparatus 1600 a includes multiple repeating pixels. The photo-detecting apparatus 1600 a includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, un-doped regions 1605 a, 1605 b are right under the control contact layers 1606 a, 1606 b. That is, the portions of the absorption layer 1602 right under the control contact layers 1606 a, 1606 b may be intrinsic or include a dopant and has a dopant profile with a peak dopant concentration below approximately 1×10¹⁵ cm⁻³. The term “intrinsic” means that the portions of the absorption layer 1602 right under the control contact layers 1606 a, 1606 b are without intentionally adding dopants. In some embodiments, the control contact layers 1606 a, 1606 b on the absorption layer 1602 may lead to formation of a Schottky contact, an Ohmic contact, or a combination thereof having an intermediate characteristic between the two, depending on various factors including the material of the absorption layer 1602, the material of the control contact layers 1606 a, 1606 b, and the impurity or defect level of the absorption layer 1602.

In some embodiments, the pixel further includes two control signals cs1, cs2 controlling the control contact layers 1606 a, 1606 b for controlling the moving direction of the electrons or holes generated by the absorbed photons in the absorption layer 1602. For example, when voltages are used, if the control signal cs1 is biased against the control signal cs2, an electric field is created between the two un-doped regions 1605 a, 1605 b right under the control contact layers 1606 a, 1606 b, and free charges drift towards one of the two un-doped region 1605 a, 1605 b depending on the direction of the electric field.

In some embodiments, the pixel includes two capacitors 1610 a, 1610 b. The readout contact layers 1608 a is electrically coupled to the capacitor 1610 a, and the readout contact layers 1608 b is electrically coupled to the capacitor 1610 b. The capacitors 1610 a, 1610 b are similar to the capacitors as described before. In some embodiments, the pixel further includes a first readout circuit and a second readout circuit electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit may include the capacitor 1610 a. The second readout circuit may include the capacitor 1610 b. The first readout circuit is electrically coupled to the readout contact layer 1608 a. The second readout circuit is electrically coupled to the readout contact layer 1608 b.

In some embodiments, the first switch includes a first doped region 1601 a in the absorption layer 1602 and under the readout contact layers 1608 a. The second switch includes a first doped region 1601 b in the absorption layer 1602 and under the readout contact layers 1608 b. In some embodiments, the first doped region 1601 a is similar to the first doped region as mentioned before, such as the first doped regions 1501 a as described in FIG. 15C. In some embodiments, the first doped region 1601 b is similar to the first doped region as mentioned before, such as the first doped regions 1501 b as described in FIG. 15C.

The pixel of the photo-detecting apparatus 1600 a further includes a channel region 1630 in the absorption layer 1602. In some embodiments, the channel region 1630 is arranged between the two switches and the second surface 1602 ss of the absorption layer 1602 along a direction substantially perpendicular to the first surface 1602 s of the absorption layer 1602.

The channel region 1630 is under the control contact layers 1606 a, 1606 b along a vertical direction D1. The channel region 1630 includes a dopant and is of a conductivity type the same as the first conductivity type of the first doped regions 1601 a, 1601 b. In some embodiments, the channel region 1630 includes a dopant and has a dopant profile with peak dopant concentration not less than 1×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the channel region 1630 is between 1×10¹⁵ cm⁻³ and 5×10¹⁷ cm⁻³. In some embodiments, the peak dopant concentration of the channel region 1630 lies in the absorption layer 1602. The channel region 1630 is a buried region in the absorption layer 1602. In some embodiments, the distance between the first surface 1602 s and the location of the channel region 1630 having the peak dopant concentration is not less than 30 nm. In some embodiments, the distance between the second surface 1602 ss and the location of the channel region 1630 having the peak dopant concentration is not less than 30 nm. In some embodiments, a distance between the first surface 1602 s of the absorption layer 1602 and a location of the channel region 1630 having the peak dopant concentration is less than a distance between the second surface 1602 ss and the location of the channel region 1630 having the peak dopant concentration.

In some embodiments, the distance between the first surface 1602 s of the absorption layer 1602 and a location of the channel region 1630 having the peak dopant concentration of the channel region 1630 is between 50 nm and 650 nm. The dopant profile of the channel region 1630 can be controlled by any suitable method, such as by implantation including providing multiple implant doses and energies. In some embodiments, a width of the channel region 1630 is greater than a distance d3 between the control contact layers 1606 a, 1606 b for lowering the leakage current between the two control contact layers 1606 a, 1606 b of the photo-detecting apparatus 1600 a. In some embodiments, the width of the channel region 1630 is between 10 nm and 500 nm.

The channel region 1630 facilitates the carriers generated from the absorption layer 1602 flowing toward the first doped region 1601 a or the first doped region 1601 b without reaching the first surface 1602 s of the absorption layer 1602. As a result, the carriers accumulated between the portions under the control contact layers 1606 a, 1606 b are less. Accordingly, the demodulation contrast is improved and the leakage current between the two control contact layers 1606 a, 1606 b of the photo-detecting apparatus 1600 a is lower.

In some embodiments, the channel region 1630 may be overlapped with the first doped regions 1601 a, 1601 b. That is, the channel region 1630 may be connected to the first doped regions 1601 a, 1601 b. If the first switch is switched on and the second switch is switched off, the carriers can be pushed to flow toward the first doped region 1601 a by biasing the first doped region 1601 b of the second switch. That is, through the voltage control, there is a disconnection between the channel region 1630 and the first doped region of the switch that is turned off for the carriers, and thus the carriers will not flow into the first doped region of the switch that is turned off.

In some embodiments, the channel region 1630 is separated from the first doped regions 1601 a, 1601 b for reducing the leakage current between the first doped regions 1601 a, 1601 b.

FIG. 16B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 b in FIG. 16B is similar to the photo-detecting apparatus 1600 a in FIG. 16A, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1603 a in the absorption layer 1602 and under the control contact layer 1606 a. The second switch further includes a second doped region 1603 b in the absorption layer 1602 and under the control contact layers 1606 b. The second doped region 1503 a is similar to the second doped region as mentioned before, such as the second doped regions 1503 a as described in FIG. 15C. The second doped region 1503 b is similar to the second doped region as mentioned before, such as the second doped regions 1503 b as described in FIG. 15C. In some embodiments, the channel region 1630 is overlapped with the second doped regions 1603 a, 1603 b. That is, the overlapped area may include the dopant of the channel region 1630 and the dopant of the second doped regions 1603 a, 1603 b, wherein the two dopants are different.

FIG. 16C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 c in FIG. 16C is similar to the photo-detecting apparatus 1600 a in FIG. 16A, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 1633 a between the absorption layer 1602 and the control contact layer 1606 a. The second switch may further include a second dielectric layer 1633 b between the absorption layer 1602 and the control contact layer 1606 b.

The first dielectric layer 1633 a prevents direct current conduction from the control contact layer 1606 a to the absorption layer 1602, but allows an electric field to be established within the absorption layer 1602 in response to an application of a voltage to the control contact layer 1606 a. The second dielectric layer 1633 b prevents direct current conduction from the control contact layer 1606 b to the absorption layer 1602 but allows an electric field to be established within the absorption layer 1602 in response to an application of a voltage to the control contact layer 1606 b. The established electric field may attract or repel charge carriers within the absorption layer 1602.

FIG. 16D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 d in FIG. 16D is similar to the photo-detecting apparatus 1600 c in FIG. 16C, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1603 a under the first dielectric layer 1633 a. The second switch further includes a second doped region 1603 b under the second dielectric layer 1633 b. The second doped regions 1603 a, 1603 b are similar to the second doped regions as mentioned before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

FIG. 16E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 e in FIG. 16E is similar to the photo-detecting apparatus 1600 a in FIG. 16A, where the difference is described below. In some embodiments, the absorption layer 1602 of the pixel includes a hinder region 1640. The hinder region 1640 is between the first doped regions 1601 a, 1601 b. The hinder region 1640 is between the first surface 1602 s and the channel region 1630.

In some embodiments, the hinder region 1640 includes a dopant and is of a conductivity type. In some embodiments, the hinder region 1640 has a dopant profile with a peak dopant concentration different from the peak dopant concentration of the channel region 1630. In some embodiments, the conductivity type of the hinder region 1640 is the same as the conductivity type of the channel region 1630, and the peak dopant concentration of the hinder region 1640 is lower than the peak dopant concentration of the channel region 1630. For example, if the photo-detecting apparatus 1600 e is configured to process the collected electrons for further application. the first doped regions 1601 b, 1601 a are of n-type, the channel region 1630 is of n-type, the hinder region 1640 is of n-type, and the peak dopant concentration of the hinder region 1640 is lower than the peak dopant concentration of the channel region 1630.

In some embodiments, the conductivity type of the hinder region 1640 is different from the conductivity type of the channel region 1630, and the peak dopant concentration of the hinder region 1640 is higher than the peak dopant concentration of the channel region 1630. In some embodiments, the peak dopant concentration of the hinder region 1640 is between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³. For example, if the photo-detecting apparatus 1600 e is configured to process the collected electrons for further application. the first doped regions 1601 b, 1601 a are of n-type, the channel region 1630 is of n-type, the hinder region 1640 is of p-type, and the peak dopant concentration of the hinder region 1640 is higher than the peak dopant concentration of the channel region 1630.

The hinder region 1640 can block the carriers to be collected from reaching the first surface 1602 s of the absorption layer 1602. As a result, a collection efficiency of the photo-detecting apparatus 1600 e can be improved.

FIG. 16F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 f in FIG. 16F is similar to the photo-detecting apparatus 1600 e in FIG. 16E, where the difference is described below. The photo-detecting apparatus 1600 f further includes a first buffer region 1661 and a second buffer region 1662. The first buffer region 1661 and the second buffer region 1662 are in the absorption layer 1602. The first buffer region 1661 is between the first doped regions 1601 a, 1601 b and is adjacent to or overlapped with the first doped region 1601 b. In some embodiments, the first buffer region 1661 is separated from the channel region 1630 for lowering the dark current of the photo-detecting apparatus 1600 f The second buffer region 1662 is between the first doped regions 1601 a, 1601 b and is adjacent to or overlapped with the first doped region 1601 a. In some embodiments, the second buffer region 1662 is separated from the channel region 1630 for lowering the dark current of the photo-detecting apparatus 1600 f. The first buffer region 1661 and the second buffer region 1662 can further modify the depletion regions in the absorption layer 1602, such as the depletion regions around the first doped regions 1601 a, 1601 b and the depletion regions near the first surface 1602 s of the absorption layer 1602.

In some embodiments, each of the first buffer region 1661 and the second buffer region 1662 has a conductivity type. In some embodiments, each of the first buffer region 1661 and the second buffer region 1662 includes a fifth dopant and has a dopant profile with a peak dopant concentration. The peak dopant concentration is not less than 1×10¹⁶ cm⁻³. In some embodiments, the peak dopant concentrations of the first buffer region 1661 and the second buffer region 1662 are lower than the peak dopant concentrations of the first doped regions 1601 b, 1601 a. In some embodiments, the peak dopant concentration of the first buffer region 1661 and the second buffer region 1662 is, for example, between 1×10¹⁶ cm⁻³ and 1×10¹⁸ cm⁻³.

Since each of the first buffer region 1661 and the second buffer region 1662 has a peak dopant concentration lower than the peak dopant concentrations of the first doped regions 1601 b, 1601 a, the reliability of the photo-detecting apparatus 1600 f can be improved.

In some embodiments, the conductivity types of the first buffer region 1661 and the second buffer region 1662 are the same as the first conductivity type of the first doped regions 1601 a, 1601 b. For example, if the photo-detecting apparatus 1600 f is configured to process the collected electrons for further application, the first doped regions 1601 a, 1601 b are of n-type, the channel region 1630 is of n-type, and the first buffer region 1661 and the second buffer region 1662 are of n-type.

The first buffer region 1661 and the second buffer region 1662 with the same conductivity type as the first conductivity type of the first doped regions 1601 a, 1601 b can improve carrier collection efficiency since the carrier collection can be confined near the first surface 1602 s of the absorption layer 1602 by the first buffer region 1661 and the second buffer region 1662.

In some embodiments, the conductivity types of the first buffer region 1661 and the second buffer region 1662 are different from the first conductivity type of the first doped regions 1601 a, 1601 b. For example, if the photo-detecting apparatus 1600 f is configured to process the collected electrons for further application, the first doped regions 1601 a, 1601 b are of n-type, the channel region 1630 is of n-type, and the first buffer region 1661 and the second buffer region 1662 are of p-type. The first buffer region 1661 blocks the carriers from flowing near the first surface 1602 s into the first doped region 1601 b, and lowers the local dark current at the same time. The second buffer region 1662 blocks the carriers from flowing near the first surface 1602 s into the first doped region 1601 a and lowers the local dark current at the same time.

The first buffer region 1661 and the second buffer region 1662 with conductivity type different from the first conductivity type of the first doped regions 1601 a, 1601 b can improve carrier collection efficiency, since the carrier collection can be confined within a region away from the first surface 1602 s of the absorption layer 1602, for example, confined at the part of the first doped region 1601 a, 1601 b farther from the first surface 1602 s of the absorption layer 1602.

In some embodiments, the first buffer region 1661 includes a depth d₅ less than a depth d₂ of the first doped region 1601 b. In some embodiments, the second buffer region 1662 includes a depth d₆ less than a depth d₂ of the first doped region 1601 a. The depth is measured from the first surface 1602 s of the absorption layer 1602 to a position where the dopant profile reaches a background concentration, such as 1×10¹⁵ cm⁻³.

FIG. 16G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 g in FIG. 16G is similar to the photo-detecting apparatus 1600 f in FIG. 16F, where the difference is described below. In some embodiments, the channel region 1630 may be overlapped with the first buffer region 1661 and the second buffer region 1662. That is, the channel region 1630 may be connected to the first buffer region 1661 and the second buffer region 1662. Since the channel region 1630 is connected to the first buffer region 1661 and the second buffer region 1662, the demodulation contrast of the photo-detecting apparatus 1600 g is improved.

FIG. 16H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 h in FIG. 16H is similar to the photo-detecting apparatus 1600 a in FIG. 16A, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1600 h further includes two counter-doped regions 1651 a, 1651 b in the absorption layer 1602. The counter-doped regions 1651 a, 1651 b are similar to the counter-doped regions as mentioned before, such as the counter-doped regions 1551 a, 1551 b as described in FIG. 15D.

FIG. 16l illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 i in FIG. 16l is similar to the photo-detecting apparatus 1600 a in FIG. 16A, where the difference is described below. In some embodiments, the photo-detecting apparatus 1600 i further includes a blocking layer 1619 surrounding the absorption layer 1602. The blocking layer 1619 is similar to the blocking layer as described before, such as the blocking layer 1519 in FIG. 15A and FIG. 15C. The photo-detecting apparatus 1600 i further includes a conductive layer 1609 electrically coupled to the blocking layer 1619. In some embodiments, the blocking layer 1619 may be biased by a bias voltage ca2 through the conductive layer 1609 to discharge the carriers not collected by the first doped regions 1601 a, 1601 b.

In some embodiments, since the channel region 1630 and blocking layer 1619 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between channel region 1630 and the blocking layer 1619, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 1602, for example, when the channel region 1630 is of n-type and the blocking layer 1619 is of p-type, the electrons tend to move toward the channel region 1630 and the holes tends to move toward the blocking layer 1619. The channel region 1630 is operated to collect the electrons and serves as a preliminary collector. The blocking layer 1619 is operated to collect the holes. The electrons stored in the channel region 1630 may further move to first doped region 1601 b or the first doped region 1601 a based on the control signals cs1, cs2. Accordingly, the demodulation contrast of the photo-detecting apparatus 1600 i is improved.

FIG. 16J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 j in FIG. 16J is similar to the photo-detecting apparatus 1600 i in FIG. 16l , where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1600 j further includes counter-doped regions 1651 a, 1651 b. The counter-doped regions 1651 a, 1651 b are similar to the counter-doped regions as mentioned before, such as the counter-doped regions 1651 a, 1651 b as described in FIG. 16H. In some embodiments, the absorption layer 1602 of the pixel includes a hinder region 1640. The hinder region 1640 is similar to the hinder region as described before, such as the hinder region 1640 as described in FIG. 16E. In some embodiments, the pixel of the photo-detecting apparatus 1600 j further includes a first buffer region 1661 and a second buffer region 1662. The first buffer region 1661 and the second buffer region 1662 are similar to the first buffer region 1661 and the second buffer region 1662 as described in FIG. 16F.

In some embodiments, if the conductivity types of the first buffer region 1661 and the second buffer region 1662 are the same as the first conductivity type of the first doped regions 1601 a, 1601 b, each of the first doped regions 1601 b, 1601 a is entirely overlapped with respective counter-doped region 1651 b, 1651 a. In some embodiments, the first buffer region 1661 is adjacent to the first doped region 1601 b or overlapped with a part of the counter-doped regions 1651 b, and the second buffer region 1662 is adjacent to the first doped region 1601 a or overlapped with a part of the counter-doped regions 1651 a. That is, a part of the first buffer region 1661 overlapped with the counter-doped regions 1651 b includes both of the fifth dopant and the dopant of the counter-doped region 1651 a, wherein the fifth dopant is different from the dopant of the counter-doped region 1651 b. The peak dopant concentration of the counter-doped regions 1651 b is lower than the peak dopant concentration of the first buffer region 1661. Similarly, a part of the second buffer region 1662 overlapped with the counter-doped regions 1651 a includes both of the dopant of the counter-doped regions 1651 a and the fifth dopant. The peak dopant concentration of the counter-doped region 1651 a is lower than the peak dopant concentration of the second buffer region 1662.

In some embodiments, the conductivity types of the first buffer region 1661 and the second buffer region 1662 are different from the first conductivity type of the first doped regions 1601 a, 1601 b, the counter-doped regions 1651 b overlaps with a portion of the first doped region 1601 b, and the counter-doped regions 1651 a overlaps with a portion of the first doped region 1601 a. That is, the part of the first doped region 1601 b farther from the first surface 1602 s of the absorption layer 1602 is neither overlapped with the counter-doped regions 1651 b nor with the first buffer region 1661, and the portion of the first doped region 1601 a farther from the first surface 1602 s of the absorption layer 1602 is neither overlapped with the counter-doped regions 1651 a nor with the second buffer region 1662.

The first buffer region 1661 and the second buffer region 1662 with conductivity type different from the first conductivity type of the first doped regions 1601 a, 1601 b can improve carrier collection efficiency, since the carrier collection can be confined within a region away from the first surface 1602 s of the absorption layer 1602, for example, confined at the part of the first doped region 1601 a farther from the first surface 1602 s of the absorption layer 1602 and neither overlapped with the counter-doped regions 1651 a nor with the second buffer region 1662; and confined at the part of the first doped region 1601 b farther from the first surface 1602 s of the absorption layer 1602 and neither overlapped with the counter-doped regions 1651 b nor with the first buffer region 1661.

FIG. 16K illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 k in FIG. 16K is similar to the photo-detecting apparatus 1600 j in FIG. 16J, where the difference is described below. In some embodiments, the photo-detecting apparatus 1600 k further includes second doped regions 1603 a, 1603 b. The second doped regions 1603 a, 1603 b are similar to the second doped regions as described before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B. In some embodiments, the first buffer region 1661 is separated from the second doped region 1603 b. In some embodiments, the second buffer region 1662 is separated from the second doped region 1603 a. In some embodiments, the first buffer region 1661, the first doped region 1601 b and the counter-doped regions 1651 b can be formed in different steps such as by different masks. The second buffer region 1662, the first doped region 1601 a and the counter-doped regions 1651 a can be formed in different steps such as by different masks.

In some embodiments, if the hinder region 1640 is of a conductivity type different from the conductivity type of the channel region 1630, the hinder region 1640 is separated from the second doped regions 1603 a, 1603 b. That is, the hinder region 1640 is not overlapped with the second doped regions 1603 a, 1603 b. In some embodiments, the width of the hinder region 1640 is less than the width of the channel region 1630.

In some embodiments, if the hinder region 1640 is of a conductivity type the same as the conductivity type of the channel region 1630, the hinder region 1640 may be connected to the second doped regions 1603 a, 1603 b. That is, the hinder region 1640 is overlapped with the second doped regions 1603 a, 1603 b.

The first buffer region 1661 and the second buffer region 1662 with the same conductivity type as the first conductivity type of the first doped regions 1601 a, 1601 b can improve carrier collection efficiency since the carrier collection can be confined near the first surface 1602 s of the absorption layer 1602 by the first buffer region 1661 and the second buffer region 1662 and since a distance between two regions with opposite conductivity types is shortened, that is, the distance between the first buffer region 1661 and the second doped region 1603 b is shorter than the distance between the first doped region 1601 b and the second doped region 1603 b; and the distance between the second buffer region 1662 and the second doped region 1603 a is shorter than the distance between the first doped region 1601 a and the second doped region 1603 a.

In some embodiments, the depth d₅ of the first buffer region 1661 is less than a depth d₁ of the second doped region 1603 b. In some embodiments, the depth d₆ of the second buffer region 1662 is less than a depth d₁ of the second doped region 1603 a.

FIG. 16L illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 16001 in FIG. 16L is similar to the photo-detecting apparatus 1600 j in FIG. 16J, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 1633 a between the absorption layer 1602 and the control contact layer 1606 a. The second switch may further include a second dielectric layer 1633 b between the absorption layer 1602 and the control contact layer 1606 b. The first dielectric layer 1633 a and the second dielectric layer 1633 b are similar to the first dielectric layer and the second dielectric layer as described before, such as the first dielectric layer 1633 a and the second dielectric layer 1633 b as described in FIG. 16C.

FIG. 16M illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1600 m in FIG. 16M is similar to the photo-detecting apparatus 16001 in FIG. 16L, where the difference is described below. In some embodiments, the photo-detecting apparatus 1600 m further includes second doped regions 1603 a, 1603 b under the first dielectric layer 1633 a and the second dielectric layer 1633 b respectively. The second doped regions 1603 a, 1603 b are similar to the second doped regions as described before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

FIG. 17A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 a includes a substrate 1704. The photo-detecting apparatus further includes a pixel including an absorption layer 1702 supported by the substrate 1704. The absorption layer 1702 is entirely over a first surface 1704 s of the substrate 1704. The pixel includes an absorbed region AR in the absorption layer 1702. The absorbed region AR is similar to the absorbed region as mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 1702. The first switch includes a control contact layer 1706 a and a readout contact layer 1708 a. The second switch includes a control contact layer 1706 b and a readout contact layer 1708 b. In some embodiments, the readout contact layers 1708 a, 1708 b are formed over a first surface 1704 s of the substrate 1704. In some embodiments, the absorption layer 1702 is between the control contact layer 1706 b, 1706 b. In some embodiments, the control contact layer 1706 b, 1706 b are disposed at two opposite sides of the absorption layer 1702. In some embodiments, a width w₁ of the absorption layer 1702 is less than a distance d₃ between the control contact layers 1706 b, 1706 b. In some embodiments, an incoming optical signal enters into the absorbed region AR from the first surface 1702 s of the absorption layer 1702. In some embodiments, the absorption layer 1702 may be intrinsic.

In some embodiments, the photo-detecting apparatus 1700 a includes multiple repeating pixels. The photo-detecting apparatus 1700 a includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 1708 a. The second readout circuit is electrically coupled to the readout contact layer 1708 b.

In some embodiments, the first switch includes a first doped region 1701 a in the substrate 1704 under the readout contact layers 1708 a. The second switch includes a first doped region 1701 b in the substrate 1704 and under the readout contact layers 1708 b. The first doped regions 1701 a, 1701 b are similar to the first doped regions as described before, such as the first doped regions 1601 a, 1601 b as described in FIG. 16A. In some embodiments, the pixel of the photo-detecting apparatus 1700 a further includes a buried region 1731 in the absorption layer 1702.

The buried region 1731 is nearer to the first surface 1704 s of the substrate 1704 than to the first surface 1702 s of the absorption layer 1702. The buried region 1731 includes a dopant and is of a conductivity type the same as the first conductivity type of the first doped regions 1701 a,1701 b. In some embodiments, the buried region 1731 includes a dopant and has a dopant profile with a peak dopant concentration not less than 1×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the buried region 1731 is between 1×10¹⁵ cm⁻³ and 5×10¹⁷ cm⁻³. In some embodiments, the peak dopant concentration of the buried region 1731 lies in the absorption layer 1702. In some embodiments, a distance between the first surface 1704 s of the substrate 1704 and a location of the buried region 1731 having the peak dopant concentration is not more than 50 nm. The dopant profile of the buried region 1731 can be controlled by any suitable method, such as by implantation including providing multiple implant doses and energies.

In some embodiments, the dopant of the buried region 1731 may diffuse through the interface between the substrate 1704 and the absorption layer 1702 to the substrate 1704. In some embodiments, a dopant concentration at the interface between the substrate 1704 and the absorption layer 1702 is not less than 1×10¹⁵ cm⁻³. Accordingly, the defects at the interface can be passivated.

In some embodiments, the pixel of the photo-detecting apparatus 1700 a further include a repel region 1741 in the absorption layer 1702. The repel region 1741 is opposite to the buried region 1731. In some embodiments, the repel region 1741 is nearer the first surface 1702 s of the absorption layer 1702 than to the first surface 1704 s of the substrate 1740. In some embodiments, the repel region 1741 is of a conductivity type different from the first conductivity type of the first doped regions 1701 a, 1701 b. In some embodiments, the repel region 1741 includes a dopant and a dopant profile with a peak dopant concentration not less than 5×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the buried region 1731 is between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³.

The repel region 1741 may repel the carriers to be collected in the absorption layer 1702, and thus the carriers are driven to move toward the substrate 1704. Accordingly, the operation speed of the photo-detecting apparatus 1700 a is improved. For example, if the photo-detecting apparatus 1700 a is configured to collects electrons, the repel region 1741 may repel the electrons and push the electrons to move toward the substrate 1704.

In some embodiments, the carriers are generated in the absorption layer 1702 and the demodulation and the collection of the carriers are in the substrate 1704.

In some embodiments, the repel region 1741 may be floated. In some embodiments, the photo-detecting apparatus 1700 a further includes a conductive layer 1710 electrically coupled to the repel region 1741. For example, the repel region 1741 may be coupled to ground through the conductive layer 1710.

In some embodiments, since the buried region 1731 and repel region 1741 in the absorption layer 1702 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between the buried region 1731 and the repel region 1741, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 1702, for example, when the buried region 1731 is of n-type and the repel region 1741 is of p-type, the electrons tend to move toward the buried region 1731 and the holes tends to move toward the repel region 1741. The buried region 1731 is operated to collect the electrons and serves as a preliminary collector. The repel region 1741 is operated to collect the holes. The electrons stored in the buried region 1731 may further move to the first doped region 1701 b or the first doped region 1701 a across the interface between the substrate 1704 and the absorption layer 1702 based on the control signals cs1, cs2. Accordingly, the demodulation contrast of the photo-detecting apparatus 1700 a is improved.

FIG. 17B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 b in FIG. 17B is similar to the photo-detecting apparatus 1700 a in FIG. 17A, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1703 a in the substrate 1704 and under the control contact layer 1706 a. The second switch further includes a second doped region 1703 b in the substrate 1704 and under the control contact layer 1706 b. The second doped regions 1703 a, 1703 b are similar to the second doped regions as described before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

FIG. 17C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 c in FIG. 17C is similar to the photo-detecting apparatus 1700 a in FIG. 17A, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 1733 a between the substrate 1704 and the control contact layer 1706 a. The second switch may further include a second dielectric layer 1733 b between the substrate 1704 and the control contact layer 1706 b. The first dielectric layer 1733 a prevents direct current conduction from the control contact layer 1706 a to the substrate 1704, but allows an electric field to be established within the substrate 1704 in response to an application of a voltage to the control contact layer 1706 a. The second dielectric layer 1733 b prevents direct current conduction from the control contact layer 1706 b to the substrate 1704 but allows an electric field to be established within the substrate 1704 in response to an application of a voltage to the control contact layer 1706 b. The established electric field may attract or repel charge carriers within the substrate 1704.

FIG. 17D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 d in FIG. 17D is similar to the photo-detecting apparatus 1700 c in FIG. 17C, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1703 a in the substrate 1704 and under the first dielectric layer 1733 a. The second switch further includes a second doped region 1703 b in the substrate 1704 and under the first dielectric layer 1733 b. The second doped regions 1703 a, 1703 b are similar to the second doped regions as mentioned before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

FIG. 17E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 e in FIG. 17E is similar to the photo-detecting apparatus 1700 a in FIG. 17A, where the difference is described below. In some embodiments, the photo-detecting apparatus 1700 e further includes a first buffer region 1761 and a second buffer region 1762 in the substrate 1704. The first buffer region 1761 and the second buffer region 1762 are similar to the first buffer region 1661 and the second buffer region 1662 as described in FIG. 16F.

The first buffer region 1761 and the second buffer region 1762 can further modify the depletion regions in the substrate 1704, such as the depletion regions around the first doped regions 1701 a, 1701 b and the depletion regions near the first surface 1704 s of the substrate 1704.

The first buffer region 1761 and the second buffer region 1762 with conductivity type different from the first conductivity type of the first doped regions 1701 a, 1701 b can improve carrier collection efficiency, since the carrier collection can be confined within a region away from the first surface 1704 s of the substrate 1704, for example, confined at the part of the first doped region 1701 a, 1701 b farther from the first surface 1704 s of the substrate 1704.

The first buffer region 1761 and the second buffer region 1762 with the same conductivity type as the first conductivity type of the first doped regions 1701 a, 1701 b can improve carrier collection efficiency since the carrier collection can be confined near the first surface 1704 s of the substrate 1704 by the first buffer region 1761 and the second buffer region 1762.

In some embodiments, the photo-detecting apparatus 1700 e may further include second doped regions (not shown) under the control contact layers 1706 a, 1706 b. The second doped regions are similar to the second doped regions described before, such as the second doped regions 1703 a, 1703 b as described in FIG. 17B. In such an embodiments, The first buffer region 1761 and the second buffer region 1762 with the same conductivity type as the first conductivity type of the first doped regions 1701 a, 1701 b can improve carrier collection efficiency since the carrier collection can be confined near the first surface 1704 s of the substrate 1704 by the first buffer region 1761 and the second buffer region 1762 and since a distance between two regions with opposite conductivity types is shortened, that is, the distance between the first buffer region 1761 and the second doped region (not shown) is shorter than the distance between the first doped region 1701 b and the second doped region (not shown); and the distance between the second buffer region 1762 and the second doped region (not shown) is shorter than the distance between the first doped region 1701 a and the second doped region (not shown).

In some embodiments, the photo-detecting apparatus 1700 e may further include a first dielectric layer and a second dielectric layer 1733 a, 1733 b as described in FIG. 17C.

FIG. 17F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 f in FIG. 17F is similar to the photo-detecting apparatus 1700 a in FIG. 17A, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1700 f further includes counter-doped regions 1751 a, 1751 b in the substrate 1704. The counter-doped regions 1751 a, 1751 b are similar to the counter-doped regions as mentioned before, such as 1651 a, 1651 b as described in FIG. 16H. Since the counter-doped region 1751 a, 1751 b overlaps with at least a portion of the first doped region 1701 a, 1701 b, the photo-detecting apparatus 1700 f has thinner depletion regions in the substrate 1704, and thus the photo-detecting apparatus 1700 f is with lower dark current.

In some embodiments, the photo-detecting apparatus 1700 f may further include a first dielectric layer and a second dielectric layer as mentioned before, such as the first dielectric layer 1733 a, and the second dielectric layer 1733 b as described in FIG. 17C.

FIG. 17G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 g in FIG. 17G is similar to the photo-detecting apparatus 1700 f in FIG. 17F, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1700 g further includes a first buffer region 1761 and a second buffer region 1762 in the substrate 1704. The first buffer region 1761 and the second buffer region 1762 are similar to the first buffer region and the second buffer region as mentioned before, such as the first buffer region 1761 and the second buffer region 1762 as described in FIG. 17E. In some embodiments, the photo-detecting apparatus 1700 g may further includes a first dielectric layer and a second dielectric layer as mentioned before, such as the first dielectric layer 1733 a, and the second dielectric layer 1733 b as described in FIG. 17C.

FIG. 17H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 h in FIG. 17H is similar to the photo-detecting apparatus 1700 a in FIG. 17A, where the difference is described below. In some embodiments, the photo-detecting apparatus 1700 h includes multiple buried regions. For example, the photo-detecting apparatus 1700 h includes a first buried region 1731 a, which is similar to the buried region 1731 as described in FIG. 17A. The pixel of the photo-detecting apparatus 1700 h further includes a second buried region 1731 b. The second buried region 1731 b is in the substrate 1704. The second buried region 1731 b is formed at the first surface 1704 s of the substrate layer 1704. The second buried region 1731 b also includes a dopant and is of a conductivity type the same as the first conductivity type of the first doped regions 1701 a, 1701 b. In some embodiments, the peak dopant concentration of the second buried region 1731 b lies in the substrate 1704. In some embodiments, a distance between the first surface 1704 s of the substrate 1704 and a location of the second buried region 1731 b having the peak dopant concentration is not more than 50 nm. In some embodiments, the dopant of the second buried region 1731 b may diffuse through the interface between the substrate 1704 and the absorption layer 1702 to the absorption layer 1702. Accordingly, the defects at the interface can be passivated. In some embodiments, a width w₂ of the second buried region 1731 b is greater than the width w₁ of the absorption layer 1702.

In some embodiments, the dopant of the first buried region 1731 a and the dopant of the second buried region 1731 a may be the same. In some embodiments, the peak dopant concentration of the first buried region 1731 a and the peak dopant concentration of the second buried region 1731 a are on the two opposite sides of the interface between the substrate 1704 and the absorption layer 1702. In some embodiments, the absorption layer 1702 may be intrinsic.

FIG. 17I illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1700 i in FIG. 17I is similar to the photo-detecting apparatus 1700 h in FIG. 17H, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1700 i further includes a first buffer region 1761 and a second buffer region 1762 in the substrate 1704. The first buffer region 1761 and the second buffer region 1762 are similar to the first buffer region and the second buffer region as mentioned before, such as the first buffer region 1761 and the second buffer region 1762 as described in FIG. 17E. In some embodiments, the pixel of the photo-detecting apparatus 1700 i further includes counter-doped regions 1751 a, 1751 b in the substrate 1704. The counter-doped regions 1751 a, 1751 b are similar to the counter-doped regions as mentioned before, such as the counter-doped regions 1751 a, 1751 b as described in FIG. 17F.

In some embodiments, the first switch of the photo-detecting apparatus 1700 i further includes a second doped region (not shown) in the substrate and under the control contact layer 1706 a. The second switch of the photo-detecting apparatus 1700 i further includes a second doped region (not shown) in the substrate 1704 and under the control contact layer 1706 b. The second doped regions 1703 a, 1703 b are similar to the second doped regions as mentioned before, such as the second doped regions 1703 a, 1703 b as described in FIG. 17B.

FIG. 18A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 a includes a substrate 1804. The photo-detecting apparatus 1800 a further includes a pixel including an absorption layer 1802 supported by the substrate 1804. The pixel includes an absorbed region AR in the absorption layer 1802. The absorbed region AR is similar to the absorbed region AR mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel further includes a carrier control layer 1810 over the absorption layer 1802. In some embodiments, the carrier control layer 1810 is over a first surface 1802 s of the absorption layer 1802. In some embodiments, the carrier control layer 1810 is epitaxially formed on the first surface 1802 s of the absorption layer 1802.

In some embodiments, the absorption layer 1802 receives an optical signal and converts the optical signal into electrical signals. In some embodiments, a material of the carrier control layer 1810 is different from a material of the absorption layer 1802.

In some embodiments, the material of the carrier control layer 1810 includes a semiconductor material. In some embodiments, the material of the absorption layer 1802 includes a semiconductor material. In some embodiments, the material of the absorption layer 1802 has a first band gap, and the material of the carrier control layer 1810 has a second band gap greater than the first band gap. In some embodiments, the carrier control layer 1810 is of a conductivity type different from a conductivity type of the absorption layer 1802. In some embodiments, the carrier control layer 1810 is of a conductivity type the same as a conductivity type of the absorption layer 1802. In some embodiments, the semiconductor material includes a group III-V semiconductor material or a group IV semiconductor material. In some embodiments, the carrier control layer 1810 includes Si, and the absorption layer 1802 includes Ge. In some embodiments, the carrier control layer 1810 includes amorphous Si, polycrystalline Si, crystalline Si, or a combination thereof.

In some embodiments, the carrier control layer 1810 and the absorption layer 1802 is a heterojunction diode. In some embodiments, the carrier control layer 1810 has a thickness less than a thickness of the absorption layer 1802. In some embodiments, the carrier control layer 1810 has a thickness not less than 100 nm, and not more than 500 nm. In some embodiments, the thickness of the carrier control layer 1810 is between 200 nm and 500 nm. In some embodiments, the photo-detecting apparatus 1800 a further includes a readout contact layer 1808 electrically coupled to the carrier control layer 1810. The readout contact layer 1808 is over a first surface 1810 s of the carrier control layer 1810. The carrier control layer 1810 may be biased through the readout contact layer 1808 by a bias voltage to control and collect carriers.

In some embodiments, the photo-detecting apparatus 1800 a includes a first doped region (not shown) under the readout contact layer 1808. The first doped region includes a first dopant and has a dopant profile with a peak dopant concentration in a range from 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The first doped region is to facilitate controlling the movement and the collection of the carriers.

In some embodiments, the first doped regions under the readout contact layer 1808 are of n-type if the photo-detecting apparatus 1800 a is configured to collect electrons.

The photo-detecting apparatus 1800 a includes multiple repeating pixels. The photo-detecting apparatus 1800 a includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the carriers generated in the absorption layer 1802 flow across the interface between the absorption layer 1802 and the carrier control layer 1810 and then flow into the carrier control layer 1810 to be controlled, such as demodulated and collected by the readout contact layer 1808 formed over the carrier control layer 1810. In this way, the scaling capability and process integration may be improved since the process afterwards can be finished on the carrier control layer 1810 rather than on the absorption layer 1802. Furthermore, since the absorption function and the carrier control function such as demodulation of the carriers and collection of the carriers operate in the absorption layer 1802 and the carrier control layer 1810 respectively, and wherein the carrier control layer 1810 has a band gap greater than the bandgap of the absorption layer 1802, the dark current of the photo-detecting apparatus 1800 a is lower.

In some embodiments, the photo-detecting apparatus 1800 a may be applied to a CMOS image sensor.

FIG. 18B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 b in FIG. 18B is similar to the photo-detecting apparatus 1800 a in FIG. 18A, where the difference is described below.

In some embodiments, the pixel of the photo-detecting apparatus 1800 b further includes a control contact layer 1806 electrically coupled to the carrier control layer 1810. The control contact layer 1806 is formed over the first surface 1810 s of the carrier control layer 1810.

In some embodiments, the photo-detecting apparatus 1800 b further includes a second doped region (not shown) right under the control contact layer 1806. The second doped region is of a conductivity type different from the conductivity type of the first doped region. In some embodiments, the second doped region includes a second dopant and has a dopant profile with dopant concentration in a range from 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. The second doped region is to facilitate collecting carriers different from the carriers collected by the readout contact layer 1808. The second doped region may be biased through the control contact layer 1806 by a bias voltage to discharge collected carriers.

FIG. 18C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 c in FIG. 18C is similar to the photo-detecting apparatus 1800 b in FIG. 18B, where the difference is described below.

In some embodiments, the photo-detecting apparatus 1800 c further includes a blocking layer 1819 surrounding at least a portion of the absorption layer 1802. The blocking layer 1819 may be similar to the blocking layer as mentioned before, such as the blocking layer 1519 as described in FIG. 15 A.

In some embodiments, the photo-detecting apparatus 1800 c further includes a conductive layer 1809 electrically connected to the blocking layer 1819 and over the first surface 1804 s of the substrate 1804. The blocking layer 1819 may be biased through the conductive layer 1809 by a bias voltage to discharge carriers.

FIG. 18D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments.

The photo-detecting apparatus 1800 d includes a substrate 1804. The photo-detecting apparatus 1800 d further includes a pixel including an absorption layer 1802 supported by the substrate 1804. The pixel includes an absorbed region AR in the absorption layer 1802. The absorbed region AR is similar to the absorbed region AR mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel further includes a carrier control layer 1810 over the absorption layer 1802. In some embodiments, the carrier control layer 1810 is over a first surface 1802 s of the absorption layer 1802. In some embodiments, the carrier control layer 1810 is epitaxially formed on the first surface 1802 s of the absorption layer 1802. The carrier control layer 1810 may be similar to the carrier control layer 1810 as described in FIG. 18A. The pixel further includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 1802. The first switch includes a control contact layer 1806 a and a readout contact layer 1808 a. The second switch includes a control contact layer 1806 b and a readout contact layer 1808 b. In some embodiments, the readout contact layers 1808 a, 1808 b and the control contact layers 1806 a, 1806 b are formed over the first surface 1810 s of the carrier control layer 1810. In some embodiments, a width of the absorbed region AR is less than a distance between the readout contact layers 1808 a, 1808 b. In some embodiments, the readout contact layers 1808 a, 1808 b are disposed at two opposite sides of the absorbed region AR.

In some embodiments, an un-doped region (not labeled) is right under the control contact layer 1806 a. Another un-doped region (not labeled) is right under the control contact layer 1806 b. That is, the portions of the carrier control layer 1810 right under the control contact layers 1806 a, 1806 b may be intrinsic or include a dopant having a peak dopant concentration below approximately 1×10¹⁵ cm⁻³. The term “intrinsic” means that the portions of the carrier control layer 1810 right under the control contact layers 1806 a, 1806 b are without intentionally adding dopants. In some embodiments, the control contact layers 1806 a, 1806 b on the carrier control layer 1810 may lead to formation of a Schottky contact, an Ohmic contact, or a combination thereof having an intermediate characteristic between the two, depending on various factors including the material of the carrier control layer 1810, the material of the control contact layers 1806 a, 1806 b, and the impurity or defect level of the carrier control layer 1810.

The pixel further includes two control signals cs1, cs2 controlling the control contact layers 1806 a, 1806 b for controlling the moving direction of the carriers in the carrier control layer 1810, wherein the carriers are generated by the absorbed photons in the absorption layer 1802. For example, when voltages are used, if the control signal cs1 is biased against the control signal cs2, an electric field is created between the two portions of the carrier control layer 1810 right under the control contact layers 1806 a, 1806 b, and free charges drift towards one of the two undoped portions of the carrier control layer 1810 right under the readout contact layers 1808 b, 1808 a depending on the direction of the electric field.

In some embodiments, the photo-detecting apparatus 1800 d includes two capacitors as mentioned before, such as the capacitors 1610 a, 1610 b as described in FIG. 16A. The capacitors are for storing the carriers generated in the absorption layer 1802 and flow into the carrier control layer 1810 based on the control of the two control signals cs1, cs2.

In some embodiments, the photo-detecting apparatus 1800 d further includes a first readout circuit and a second readout circuit electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit may include one of the capacitors. The second readout circuit may include the other capacitor. The first readout circuit is electrically coupled to the readout contact layer 1808 a. The second readout circuit is electrically coupled to the readout contact layer 1808 b.

The photo-detecting apparatus 1800 d includes multiple repeating pixels. The photo-detecting apparatus 1800 d includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, the carriers generated in the absorption layer 1802 flow across the interface between the absorption layer 1802 and the carrier control layer 1810 and then flow into the carrier control layer 1810 to be controlled, such as demodulated and collected by the control contact layers 1806 a, 1806 b and the readout contact layers 1808 b, 1808 a. In this way, the scaling capability and process integration may be improved since the process afterwards can be finished on the carrier control layer 1810 rather than on the absorption layer 1802. Furthermore, since the absorption function and the carrier control function such as demodulation of the carriers and collection of the carriers operate separately in the absorption layer 1802 and the carrier control layer 1810 respectively, and wherein the carrier control layer 1810 has a band gap greater than the bandgap of the absorption layer 1802, the dark current of the photo-detecting apparatus 1800 d is lower.

FIG. 18E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 e in FIG. 18E is similar to the photo-detecting apparatus in FIG. 18D, where the difference is described below. In some embodiments, the photo-detecting apparatus 1800 e further includes a blocking layer 1819. The blocking layer 1819 may be similar to the blocking layer as mentioned before, such as the blocking layer 1519 as described in FIG. 15 A. In some embodiments, the photo-detecting apparatus 1800 e further includes a conductive layer 1809 electrically connected to the blocking layer 1819. The blocking layer 1819 may be biased through the conductive layer 1809 by a bias voltage to discharge carriers.

FIG. 18F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 f in FIG. 18F is similar to the photo-detecting apparatus 1800 e in FIG. 18E, where the difference is described below. In some embodiments, the first switch includes a first doped region 1801 a under the readout contact layer 1808 a and in the carrier control layer 1810. The second switch includes a first doped region 1801 b under the readout contact layers 1808 b and in the carrier control layer 1810. In some embodiments, the first doped regions 1801 a, 1801 b are each of a first conductivity type. In some embodiments, the first doped regions 1801 a, 1801 b include a first dopant. The peak dopant concentrations the first doped regions 1801 a, 1801 b depend on the material of the readout contact layers 1808 a, 1808 b and the material of the carrier control layer 1810, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, the peak dopant concentrations of the first doped regions 1801 a, 1801 b lie in the carrier control layer 1810. The first doped regions 1801 a, 1801 b are for collecting the carriers generated and flow from the absorption layer 1802, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2.

FIG. 18G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 g in FIG. 18G is similar to the photo-detecting apparatus 1800 f in FIG. 18F, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1803 a under the control contact layers 1806 a. The second switch further includes a second doped region 1803 b under the control contact layers 1806 b. The second doped regions 1803 a, 1803 b are in the carrier control layer 1810. In some embodiments, the second doped regions 1803 a, 1803 b are each of a second conductivity type different from the conductivity type of the first doped regions 1801 b, 1801 a. In some embodiments, each of the second doped regions 1803 a, 1803 b includes a second dopant. The peak dopant concentrations of the second doped regions 1803 a, 1803 b depend on the material of the control contact layers 1806 b, 1806 a and the material of the carrier control layer 1810, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, the peak dopant concentrations of the second doped regions 1801 a, 1801 b lie in the carrier control layer 1810. The second doped regions 1803 a, 1803 b forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 1806 b, 1806 a. The second doped regions 1803 a, 1803 b are for demodulating the carriers generated and flow from the absorption layer 1802 based on the control of the control signals cs1, cs2. In some embodiments, the depth d2 of each of the first doped regions 1801 a, 1801 b and the depth d1 of each of the second doped regions 1803 a, 1803 b is less than a thickness of the carrier control layer 1810. The depth is measured from the first surface 1810 s of the carrier control layer 1810 to a position where the dopant profile reaches a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the parts of the interface between the carrier control layer 1810 and the absorption layer 1802 and under second doped regions 1803 a,1803 b are of or lower than a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the parts of the interface between the carrier control layer 1810 and the absorption layer 1802 and under the first doped regions 1801 a, 1801 b are of or lower than a background concentration, such as 1×10¹⁵ cm⁻³.

In some embodiment, since the absorption function and the carrier control function such as demodulation of the carriers and collection of the carriers operate separately in the absorption layer 1802 and the carrier control layer 1810 respectively, and wherein the carrier control layer 1810 has a band gap greater than the bandgap of the absorption layer 1802, the leakage current between the two control contact layers 1806 a, 1806 b of the photo-detecting apparatus 1800 g is lower.

FIG. 18H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 h in FIG. 18H is similar to the photo-detecting apparatus 1800 f in FIG. 18F, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 1833 a between the carrier control layer 1810 and the control contact layer 1806 a. The second switch may further include a second dielectric layer 1833 b between the carrier control layer 1810 and the control contact layer 1806 b. The first dielectric layer 1833 a prevents direct current conduction from the control contact layer 1806 a to the carrier control layer 1810, but allows an electric field to be established within the carrier control layer 1810 in response to an application of a voltage to the control contact layer 1806 a. The second dielectric layer 1833 b prevents direct current conduction from the control contact layer 1806 b to the carrier control layer 1810 but allows an electric field to be established within the carrier control layer 1810 in response to an application of a voltage to the control contact layer 1806 b. The established electric field may attract or repel charge carriers within the carrier control layer 1810, wherein the charge carriers are generated and flow from the absorption layer 1802.

FIG. 18I illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 i in FIG. 18I is similar to the photo-detecting apparatus 1800 h in FIG. 18H, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1803 a under the first dielectric layer 1833 a. The second switch further includes a second doped region 1803 b under the second dielectric layer 1833 b. The second doped regions 1803 a, 1803 b are similar to the second doped regions 1803 a, 1803 b as described in FIG. 18G.

FIG. 18J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 j in FIG. 18J is similar to the photo-detecting apparatus 1800 g in FIG. 18G, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 1800 j further includes two counter-doped regions 1851 a, 1851 b in the carrier control layer 1810. The counter-doped regions 1851 a, 1851 b are similar to the counter-doped regions as mentioned before, such as the counter-doped region 1551 a, 1551 b as described in FIG. 15D. In some embodiments, the peak dopant concentrations of the counter-doped region 1851 a, 1851 b lie in the carrier control layer 1810. In some embodiments, the dopants of the counter-doped region 1851 a, 1851 b may diffuse into the absorption layer 1802. The counter-doped regions 1851 a, 1851 b serve as dark-current reduction regions for reducing the dark current of the photo-detecting apparatus 1800 j. Compared to a photo-detecting apparatus devoid of counter-doped region 1851 a, 1851 b, the photo-detecting apparatus 1800 j including counter-doped region 1851 a, 1851 b overlapped with at least a portion of the first doped region 1801 a,1801 b has thinner depletion regions in the carrier control layer 1810, and thus the photo-detecting apparatus 1800 j is with lower dark current.

FIG. 18K illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 k in FIG. 18K is similar to the photo-detecting apparatus 1800 j in FIG. 18J, where the difference is described below. The pixel of the photo-detecting apparatus 1800 k further includes a first buffer region 1861 and a second buffer region 1862. The first buffer region 1861 and the second buffer region 1862 are in the carrier control layer 1810. The first buffer region 1861 and the second buffer region 1862 are similar to the first buffer region and the second buffer region mentioned before, such as the first buffer region 1661 and the second buffer region 1662 as described in FIG. 16J. In some embodiments, the peak dopant concentrations of the first buffer region 1861 and the second buffer region 1862 lie in the carrier control layer 1810.

The first buffer region 1861 and the second buffer region 1862 can further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

In some embodiments, as similarly described in FIG. 16J, the conductivity types of the first buffer region 1861 and the second buffer region 1862 are the same as the first conductivity type of the first doped regions 1801 a, 1801 b. The first buffer region 1861 and the second buffer region 1862 with the same conductivity type as the first conductivity type of the first doped regions 1801 a, 1801 b can improve carrier collection efficiency since the carrier collection can be confined near the first surface 1810 s of the carrier control layer 1810 by the first buffer region 1861 and the second buffer region 1862 and since a distance between two regions with opposite conductivity types is shortened, that is, the distance between the first buffer region 1861 and the second doped region 1803 b is shorter than the distance between the first doped region 1801 b and the second doped region 1803 b; and the distance between the second buffer region 1862 and the second doped region 1803 a is shorter than the distance between the first doped region 1801 a and the second doped region 1803 a.

In some embodiments, as similarly described in FIG. 16J, the conductivity types of the first buffer region 1861 and the second buffer region 1862 are different from the first conductivity type of the first doped regions 1801 a, 1801 b. For example, if the photo-detecting apparatus 1800 k is configured to process the collected electrons for further application, the first doped regions 1801 a, 1801 b are of n-type, the second doped regions 1803 a, 1803 b are of p-type, the counter-doped regions 1851 a, 1851 b are of p-type, and the first buffer region 1861 and the second buffer region 1862 are of p-type. The first buffer region 1861 blocks the carriers from flowing near the first surface 1810 s of the carrier control layer 1810 into the first doped region 1801 b, and lowers the local dark current at the same time. The second buffer region 1862 blocks the carriers from flowing near the first surface 1810 s of the carrier control layer 1810 into the first doped region 1801 a, and lowers the local dark current at the same time.

In some embodiments, the counter-doped regions 1851 b overlaps with only a portion of the first doped region 1801 b, that is, a portion of the first doped region 1801 b farther from the first surface 1810 s of the carrier control layer 1810 is neither overlapped with the counter-doped regions 1851 b nor with the first buffer region 1861. In some embodiments, the counter-doped regions 1851 a overlaps with only a portion of the first doped region 1801 a, that is, a portion of the first doped region 1801 a farther from the first surface 1810 s of the carrier control layer 1810 is neither overlapped with the counter-doped regions 1851 a nor with the second buffer region 1862.

The first buffer region 1861 and the second buffer region 1862 with conductivity type different from the first conductivity type of the first doped regions 1801 a, 1801 b can improve carrier collection efficiency, since the carrier collection can be confined within a region away from the first surface 1810 s of the carrier control layer 1810, for example, confined at the portion of the first doped region 1801 a farther from the first surface 1810 s of the carrier control layer 1810 and neither overlapped with the counter-doped regions 1851 a nor with the second buffer region 1862; and confined at the portion of the first doped region 1801 b farther from the first surface 1810 s of the carrier control layer 1810 and neither overlapped with the counter-doped regions 1851 b nor with the first buffer region 1861.

In some embodiments, as similarly described in FIG. 16k , the first buffer region 1861 includes a depth d₅ less than a depth d₂ of the first doped region 1801 b. In some embodiments, the depth d₅ of the first buffer region 1861 is less than a depth d₁ of the second doped region 1803 b. In some embodiments, the second buffer region 1862 includes a depth d₆ less than a depth d₂ of the first doped region 1801 a. In some embodiments, the depth d₆ of the second buffer region 1862 is less than a depth d₁ of the second doped region 1803 a.

FIG. 18L illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 18001 in FIG. 18L is similar to the photo-detecting apparatus 1800 g in FIG. 18G, where the difference is described below. The pixel of the photo-detecting apparatus 18001 further includes barrier regions 1820 a, 1820 b. In some embodiments, a part of the barrier region 1820 a is in the absorption layer 1802. A part of the barrier region 1820 b is in the absorption layer 1802. In some embodiments, the barrier region 1820 a is formed in both of the absorption layer 1802 and the carrier control layer 1810. The barrier region 1820 b is formed in both of the absorption layer 1802 and the carrier control layer 1810. The barrier regions 1820 a, 1820 b cover a part of the interface between the carrier control layer 1810 and the absorption layer 2002.

In some embodiments, the barrier region 1820 a is between the first switch and the second surface 1802 ss′. In some embodiments, the barrier region 1820 a is partially under the first doped region 1801 a along a vertical direction D1. The barrier region 1820 b is between the second switch and the second surface 1802 ss′. In some embodiments, the barrier region 1820 b is partially under the first doped region 1801 b along a vertical direction D1. In some embodiments, the barrier region 1820 a is partially under the second doped region 1803 a along a vertical direction D1. The barrier region 1820 b is partially under the second doped region 1803 b along a vertical direction D1. In some embodiments, a width w3 of the absorbed region AR is greater than a distance d3 between the control contact layers 1806 a, 1806 b. In some embodiments, the width w3 of the absorbed region AR is shorter than a distance w4 between the outer sides of the barrier regions 1820 a and 1820 b.

In some embodiments, each of the barrier regions 1820 a, 1820 b is of a conductivity type different from the first conductivity type of the first doped regions 1801 a, 1801 b. In some embodiments, each of the barrier regions 1820 a, 1820 b includes a dopant and has a dopant profile with a peak dopant concentration. The peak dopant concentration is lower than the peak dopant concentrations of the first doped regions 1801 b, 1801 a. In some embodiments, the peak dopant concentration of the barrier regions 1820 a, 1820 b is, for example, not more than 1×10¹⁸ cm⁻³. In some embodiments, a concentration at the interface between the absorption layer 1802 and the carrier control layer 1810 and covered by the barrier regions 1820 a, 1820 b is not less than 1×10¹⁵ cm⁻³.

In some embodiments, the barrier regions 1820 a, 1820 b include a material different from the material of the absorption layer 1802 and different from the material of the carrier control layer 1810. In some embodiments, the barrier regions 1820 a, 1820 b include an insulating material to serve as a region of high electrical resistance between absorbed region AR and the first doped regions 1801 a, 1801 b.

In some embodiments, the barrier regions 1820 a, 1802 b are capable of confining a path for the carriers, which are generated in the absorption layer 1802, and then flowing to the carrier control layer 1810. As a result, the absorbed region AR can be enlarged compared to a photo-detecting apparatus devoid of the barrier regions, and thus more carriers can be generated in the absorbed region AR and then flow into the carrier control layer 1810 through the path confined between the barrier regions 1820 a, 1802 b. Furthermore, the barrier regions 1820 a, 1802 b can also block the dark current generated in the absorption layer 1802. Accordingly, the demodulation contrast of the photo-detecting apparatus 18001 is improved and the dark current of the photo-detecting apparatus 18001 can be reduced at the same time.

In some embodiments, the photo-detecting apparatus 18001 also includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K.

In some embodiments, the photo-detecting apparatus 18001 also includes counter-doped regions 1851 a, 1851 b as described in FIG. 18J.

FIG. 18M illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 m in FIG. 18M is similar to the photo-detecting apparatus 1800 g in FIG. 18G, where the difference is described below.

The pixel of the photo-detecting apparatus 1800 m further includes a third doped region 1817 in the carrier control layer 1810 and between the first switch and the second switch. In some embodiments, the third doped region 1817 is between the second doped regions 1803 a,1803 b. The third doped region 1817 is of a third conductivity type the same as the first conductivity type of the first doped regions 1801 b, 1801 a. In some embodiments, the third doped region 1817 includes a dopant and a dopant profile with a peak dopant concentration lower than the peak dopant concentration of the first doped regions 1801 b, 1801 a. In some embodiments, the peak dopant concentration of the third doped region 1817 is not more than 1×10¹⁸ cm⁻³. In some embodiments, the peak dopant concentration of the third doped region 1817 lies in the carrier control layer 1810. In some embodiments, the dopant of the third doped region 1817 may diffuse into the absorption layer 1802.

Since the third doped region 1817 and blocking layer 1819 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between third doped region 1817 and the blocking layer 1819, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 1802, for example, when the third doped region 1817 is of n-type and the blocking layer 1819 is of p-type, the electrons tend to move toward the third doped region 1817 and the holes tends to move toward the blocking layer 1819. The third doped region 1817 is operated to collect the electrons and the blocking layer 1819 is operated to collect the holes. The third doped region 1817 serves as a preliminary collector. The electrons stored in the third doped region 1817 may then move to the first doped region 1801 b or the first doped region 1801 a based on the control signals cs1, cs2.

In some embodiments, the carriers generated in the absorption layer 1802 may have difficulty flowing from the absorption layer 1802 to the carrier control layer 1810 through the interface there between due to the band gap difference between the absorption layer 1802 and the carrier control layer 1810. The third doped region 1817 serves as a channel to attract the carriers. As a result, the absorbed region AR may also be enlarged since the carriers generated in the absorption layer 1802 will flow concentratedly toward the third doped region 1817 and then into the carrier control layer 1810. Therefore, the quantum efficiency of the photo-detecting apparatus 1800 m is higher and the amount of the carriers moving toward the first doped region 1801 b or the first doped region 1801 a is also higher.

In some embodiments, the photo-detecting apparatus 1800 m may also include the barrier regions 1820 a, 1802 b as described in FIG. 18L to further confine the flow of the carriers in a certain path.

In some embodiments, the photo-detecting apparatus 1800 m also includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K to further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

In some embodiments, the photo-detecting apparatus 1800M also includes counter-doped regions 1851 a, 1851 b as described in FIG. 18J to further lower the dark current of the photo-detecting apparatus 1800M.

FIG. 18N illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 n in FIG. 18N is similar to the photo-detecting apparatus 1800 m in FIG. 18M, where the difference is described below. The carrier control layer 1810 of the pixel further includes a hinder region 1840. The hinder region 1840 is between the first switch and the second switch. In some embodiments, the hinder region 1840 is between the second doped regions 1803 a, 1803 b and is closer to the first surface 1810 s of the carrier control layer 1810 than the third doped region 1817. The hinder region 1840 is separated from the second doped regions 1803 a, 1803 b.

In some embodiments, the hinder region 1840 is overlapped with the third doped region 1817 along a vertical direction D1. In some embodiments, the hinder region 1840 includes a dopant and is of a conductivity type different from the third conductivity type of the third doped region 1817. In some embodiments, the hinder region 1840 includes a dopant and has a dopant profile with a peak dopant concentration higher than the peak dopant concentration of the third doped region 1817. In some embodiments, the peak dopant concentration of the hinder region 1840 is between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³.

The hinder region 1840 can block the carriers to be collected from reaching the first surface 1810 s of the carrier control layer 1810. As a result, a surface leakage current between the two second doped regions 1803 a, 1803 b of the photo-detecting apparatus 1800 n is reduced.

In some embodiments, the photo-detecting apparatus 1800 n may also include the barrier regions 1820 a, 1802 b as described in FIG. 18L to further confine the flow of the carriers in a certain path.

In some embodiments, the photo-detecting apparatus 1800 n also includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K to further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

In some embodiments, the photo-detecting apparatus 1800 n also includes counter-doped regions 1851 a, 1851 b as described in FIG. 18J to further lower the dark current of the photo-detecting apparatus 1800 n.

FIG. 18O illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 o in FIG. 18O is similar to the photo-detecting apparatus 1800 m in FIG. 18M, where the difference is described below. The pixel of the photo-detecting apparatus 1800 o further includes a channel region 1830 in the carrier control layer 1810. The channel region 1830 is under the control contact layers 1806 a, 1806 b along a vertical direction D1. In some embodiments, the carrier control layer 1810 is under the second doped regions 1803 a, 1803 b along a vertical direction D1. The channel region 1830 includes a dopant and is of a conductivity type the same as the first conductivity type of the first doped regions 1801 a, 1801 b. In some embodiments, the channel region 1830 includes dopant and has a dopant profile with a peak dopant concentration not less than 1×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the channel region 1830 is between 1×10¹⁵ cm⁻³ and 5×10¹⁷ cm⁻³. In some embodiments, the peak dopant concentration of the channel region 1830 lies in the carrier control layer 1810. In some embodiments, a distance between the first surface 1810 s of the carrier control layer 1810 and the location of the channel region 1830 having the peak dopant concentration is not less than 30 nm. The channel region 1830 facilitates the carriers generated from the absorption layer 1802 flowing toward the first doped regions 1801 a, 1801 b without reaching the first surface 1810 s of the carrier control layer 1810. Accordingly, the demodulation contrast is improved and the leakage current between the two control contact layers 1806 a, 1806 b of the photo-detecting apparatus 1800 o is lower.

In some embodiments, the channel region 1830 is overlapped with the second doped regions 1803 a, 1803 b.

In some embodiments, the channel region 1830 may be overlapped with the first doped regions 1801 a, 1801 b. That is, the channel region 1830 can be connected to the first doped regions 1801 a, 1801 b. If the first switch is switched on and the second switch is switched off, the carriers can be pushed to flow toward the first doped region 1801 a by biasing the first doped region 1801 b of the second switch. That is, through the voltage control, there is a disconnection between the channel region 1830 and the first doped region 1801 a of the switch that is turned off for the carriers, and thus the carriers will not flow into the first doped region of the switch that is turned off.

In a combination of the third doped region 1817 and the channel region 1830, the carriers generated in the absorption layer 1802 concentratedly flow toward the third doped region 1817 and move toward one of the first doped regions 1801 a,1801 b through the channel region 1830 based on the control of the two control signals cs1, cs2.

In some embodiments, the photo-detecting apparatus 1800 o may also include the barrier regions 1820 a, 1802 b as described in FIG. 18L to further confine the flow of the carriers in a certain path.

In some embodiments, the photo-detecting apparatus 1800 o also includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K to further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

In some embodiments, the photo-detecting apparatus 1800 o also includes counter-doped regions 1851 a, 1851 b as described in FIG. 18J to further lower the dark current of the photo-detecting apparatus 1800 o.

In some embodiments, the carrier control layer 1810 of the pixel further includes a hinder region 1840 as described in FIG. 18N to block the carriers from reaching the first surface 1810 s.

FIG. 18P illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 p in FIG. 18P is similar to the photo-detecting apparatus 1800 f in FIG. 18F, where the difference is described below. The pixel of the photo-detecting apparatus 1800 p further includes a shallow channel region 1831 in the carrier control layer 1810. The shallow channel region 1831 is under the control contact layers 1806 a, 1806 b along a vertical direction D1. The shallow channel region 1831 includes a dopant and is of a conductivity type the same as the first conductivity type of the first doped regions 1801 a, 1801 b. In some embodiments, the shallow channel region 1831 includes a dopant profile with a peak dopant concentration not less than 1×10¹⁵ cm⁻³. In some embodiments, the peak dopant concentration of the shallow channel region 1831 is between 1×10¹⁵ cm⁻³ and 5×10¹⁷ cm⁻³. In some embodiments, the peak dopant concentration of the shallow channel region 1831 lies in the carrier control layer 1810. In some embodiments, a distance between the first surface 1810 s and the location of the shallow channel region 1831 having the peak dopant concentration is less than 30 nm. The shallow channel region 1831 can attract the carriers generated in the absorption layer 1802 and also further confine the carriers flowing toward one of the first doped regions 1801 a, 1801 b based on the control of the two control signals cs1, cs2.

Accordingly, the demodulation contrast of the photo-detecting apparatus 1800 p is improved and the leakage current between the two control contact layers 1806 a, 1806 b of the photo-detecting apparatus 1800 p is lower.

In some embodiments, the pixel of the photo-detecting apparatus 1800 p further includes a third doped region 1817 in the carrier control layer 1810 and between the first switch and the second switch. The third doped region 1817 is similar to the third doped region 1817 as described in FIG. 18M. The third doped region 1817 serves as a vertical channel to further attract the carriers generated from the absorption layer 1802.

In some embodiments, the pixel of the photo-detecting apparatus 1800 p further includes barrier regions 1820 a, 1820 b as described FIG. 18L to further confine the flow of the carriers in a certain path. In some embodiments, since the barrier regions 1820 a, 1820 b block the flow of the carriers and since the third doped region 1817 attracts the carriers, the carriers generated in the absorption layer 1802 concentratedly flow toward the third doped region 1817 and move toward one of the first doped regions 1801 a, 1801 b through the shallow channel region 1831 based on the control of the two control signals cs1, cs2. The absorbed region AR can be enlarged since photo-detecting apparatus 1800 p includes the barrier regions 1820 a, 1820 b and the third doped region 1817.

In some embodiments, the pixel of the photo-detecting apparatus 1800 p further includes counter-doped regions 1851 a, 1851 b as described FIG. 18J to further lower the dark current of the photo-detecting apparatus 1800 p.

In some embodiments, the pixel of the photo-detecting apparatus 1800 p further includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K to further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

FIG. 18Q illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 q in FIG. 18Q is similar to the photo-detecting apparatus 1800 o in FIG. 18O, where the difference is described below.

In some embodiments, the carrier control layer 1810 of the pixel further includes a hinder region 1840 as described in FIG. 18N to block the carriers to be collected from reaching the first surface 1810 s.

In some embodiments, the pixel of the photo-detecting apparatus 1800 q further includes barrier regions 1820 a, 1820 b as described FIG. 18L to further confine the flow of the carriers in a certain path.

In some embodiments, the pixel of the photo-detecting apparatus 1800 q further includes a first buffer region 1861 and a second buffer region 1862 as described in FIG. 18K to further modify the depletion regions near the first surface 1810 s of the carrier control layer 1810.

In some embodiments, the pixel of the photo-detecting apparatus 1800 q further includes counter-doped regions 1851 a, 1851 b as described FIG. 18J to further lower the dark current of the photo-detecting apparatus 1800 q.

FIG. 18R illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 r in FIG. 18R is similar to the photo-detecting apparatus 1800 p in FIG. 18P, where the difference is described below. The first switch further includes a first dielectric layer 1833 a between the shallow channel region 1831 and the control contact layer 1806 a. The second switch may further include a second dielectric layer 1833 b between the shallow channel region 1831 and the control contact layer 1806 b. The first dielectric layer 1833 a and the second dielectric layer 1833 b are similar to the first dielectric layer 1833 a and the second dielectric layer 1833 b respectively as described in FIG. 18H.

FIG. 18S illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 s in FIG. 18S is similar to the photo-detecting apparatus 1800 q in FIG. 18Q, where the difference is described below. The first switch further includes a first dielectric layer 1833 a between the second doped region 1803 a and the control contact layer 1806 a. The second switch may further include a second dielectric layer 1833 b between the second doped region 1803 b and the control contact layer 1806 b. The first dielectric layer 1833 a and the second dielectric layer 1833 b are similar to the first dielectric layer 1833 a and the second dielectric layer 1833 b respectively as described in FIG. 18H.

FIG. 18T illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 t in FIG. 18T is similar to the photo-detecting apparatus 1800 e in FIG. 18E, where the difference is described below.

The photo-detecting apparatus 1800 t further includes a first conductive layer 1811 over the first surface 1810 s of the carrier control layer 1810. In some embodiments, the first conductive layer 1811 is between the control contact layers 1806 a, 1806 b. The first conductive layer 1811 can be biased by a bias voltage to reduce the leakage current of the photo-detecting apparatus 1800 t.

In some embodiments, the photo-detecting apparatus 1800 t further includes a modification contact layer 1812 a over the first surface 1810 s of the carrier control layer 1810. In some embodiments, the readout contact layer 1808 a is between the control contact layers 1806 a and the modification contact layer 1812 a from a cross-sectional view. The photo-detecting apparatus 1800 t further includes a modification contact layer 1812 b over the first surface 1810 s of the carrier control layer 1810. In some embodiments, the readout contact layer 1808 b is between the control contact layers 1806 b and the modification contact layer 1812 b from a cross-sectional view.

In some embodiments, the modification contact layers 1812 a, 1812 b can be each biased by a bias voltage to shape the electric field in the carrier control layer 1810. Accordingly, the dark current of the photo-detecting apparatus 1800 t is lower. The modification contact layer 1812 a is for shaping the electric field near the first switch. The modification contact layer 1812 b is for shaping the electric field near the second switch.

FIG. 18U illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1800 u in FIG. 18U is similar to the photo-detecting apparatus 1800 t in FIG. 18T, where the difference is described below.

The first switch further includes a first dielectric layer 1833 a between the carrier control layer 1810 and the control contact layer 1806 a. The second switch may further include a second dielectric layer 1833 b between the carrier control layer 1810 and the control contact layer 1806 b. The first dielectric layer 1833 a and the second dielectric layer 1833 b are similar to the first dielectric layer 1833 a and the second dielectric layer 1833 b respectively as described in FIG. 18H.

The photo-detecting apparatus 1800 u further includes a third dielectric layer 1834 a between the carrier control layer 1810 and the modification contact layers 1812 a. The photo-detecting apparatus 1800 u further includes a fourth dielectric layer 1834 b between the carrier control layer 1810 and the modification contact layers 1812 b.

In some embodiments, the photo-detecting apparatus 1800 u further includes a fifth dielectric layer 1832 between the carrier control layer 1810 the first conductive layer 1811.

In some embodiments, the photo-detecting apparatus 1800 u further includes the first doped regions 1801 a, 1801 b as described FIG. 18L. In some embodiments, the photo-detecting apparatus 1800 u further includes the second doped regions 1803 a, 1803 b as described FIG. 18L.

In some embodiments, the pixel of photo-detecting apparatus 1800 u further includes the barrier regions 1820 a, 1820 b as described FIG. 18L.

In some embodiments, the pixel of the photo-detecting apparatus 1800 u further includes the counter-doped regions 1851 a, 1851 b as described FIG. 18K.

In some embodiments, the pixel of the photo-detecting apparatus 1800 u further includes the first buffer region 1861 and the second buffer region 1862 as described FIG. 18K.

In some embodiments, the pixel of the photo-detecting apparatus 1800 u further includes the third doped region 1817 as described in FIG. 18M,

In some embodiments, the pixel of the photo-detecting apparatus 1800 u further includes the hinder region 1840 as described in FIG. 18N,

In some embodiments, the pixel of the photo-detecting apparatus 1800 u further includes the channel region 1830 as described in FIG. 18O or a shallow channel region 1831 as described in FIG. 18P.

In some embodiment, the photo-detecting apparatus in FIG. 18D-18U may further include two first silicide regions, and each of the first silicide regions is under the respective readout contact layer 1808 a, 1808 b. The first silicide regions are in the carrier control layer 1810 and may be similar to the first silicide regions 513 a′, 513 b′ as described in FIG. 5B. In some embodiment, the photo-detecting apparatus in FIG. 18D-18G, 18J-18Q, 18T may further include two second silicide regions under the respective control contact layer 1806 a, 1806 b. The second silicide regions are in the carrier control layer 1810 and may be similar to the second silicide regions 515 a′, 515 b′ as described in FIG. 5B.

The combination of the elements is within the scope of the present disclosure as long as the person having ordinary skill in the technical field can produce.

FIG. 19A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1900 a includes a substrate 1904. The photo-detecting apparatus 1900 a further includes a pixel including an absorption layer 1902 supported by the substrate 1904. The pixel includes an absorbed region AR in the absorption layer 1902. The absorbed region AR is similar to the absorbed region as mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 1902. The first switch includes a control contact layer 1906 a and a readout contact layer 1908 a. The second switch includes a control contact layer 1906 b and a readout contact layer 1908 b. The first switch further includes a first doped region 1901 a under the readout contact layer 1908 a. The second switch further includes a first doped region 1901 b under the readout contact layer 1908 b. In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 1908 a. The second readout circuit is electrically coupled to the readout contact layer 1908 b.

The control contact layers 1906 a, 1906 b are similar to the control contact layers as mentioned before, such as the control contact layers 1606 a, 1606 b as described in FIG. 16A. The readout contact layer 1908 b, 1908 a are similar to the readout contact layer as described before, such as the readout contact layer 1608 a, 1608 b as described in FIG. 16A. The first doped regions 1901 b, 1901 a are similar to the first doped regions as mentioned before, such as the first doped regions 1601 a, 1601 b as described in FIG. 16A.

In some embodiments, the photo-detecting apparatus 1900 a further includes a blocking layer 1919 similar to the blocking layer as mentioned before, such as the blocking layer 1519 as described in FIG. 15A and FIG. 15C.

In some embodiments, the pixel of the photo-detecting apparatus 1900 a further includes a third doped region 1917 similar to the third doped region 617′ described in FIG. 6G.

In some embodiments, the pixel of the photo-detecting apparatus 1900 a further includes a hinder region 1940 similar to the hinder region 640 described in FIG. 6L.

In some embodiments, the photo-detecting apparatus 1900 a further includes a conductive layer 1909 electrically coupled to the blocking layer 1919 to bias the blocking layer 1919.

The photo-detecting apparatus 1900 a further includes a conductive layer 1909 electrically coupled to the blocking layer 1919.

In some embodiments, the pixel of the photo-detecting apparatus 1900 a further includes two counter-doped regions 1951 a, 1951 b in the absorption layer 1902. The counter-doped regions 1951 a, 1951 b are similar to the counter-doped regions as mentioned before, such as the counter-doped regions 1551 a, 1551 b as described in FIG. 15D.

In some embodiments, the pixel of the photo-detecting apparatus 1900 a further includes a first buffer region 1961 and a second buffer region 1962. The first buffer region 1961 and the second buffer region 1962 are in the absorption layer 1902. The first buffer region 1961 and the second buffer region 1962 are similar to the first buffer region 1661 and the second buffer region 1662 respectively as described in FIG. 16F. The first buffer region 1961 and the second buffer region 1962 can further modify the depletion regions near the first surface 1902 s of the absorption layer 1902.

In some embodiments, the photo-detecting apparatus 1900 a further includes a conductive layer (not shown) on the first surface 1902 s of the absorption layer 1902 and electrically coupled to the hinder region 1940.

In some embodiments, as mentioned before, the first buffer region 1961 includes a depth d₅ less than a depth d₂ of the first doped region 1901 b, the second buffer region 1962 includes a depth d₆ less than a depth d₂ of the first doped region 1901 a.

FIG. 19B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1900 b in FIG. 19B is similar to the photo-detecting apparatus 1900 a in FIG. 19A, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1903 a under the control contact layers 1906 a. The second switch further includes a second doped region 1903 b under the control contact layers 1906 b. The second doped regions 1903 a, 1903 b are similar to the second doped regions as mentioned before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

In some embodiments, the third doped region 1917 overlaps with a portion of the second doped region 1903 a farther from the first doped region 1901 a of the first switch. The third doped region 1917 also overlaps with a portion of the second doped region 1903 b farther from the first doped region 1901 b of the second switch. In some embodiments, the entire second doped regions 1903 a, 1903 b are overlapped with the third doped region 1917 and are separated from the first buffer region 1961 and the second buffer region 1962.

In some embodiments, as mentioned before, the depth d₅ of the first buffer region 1961 is less than a depth d₁ of the second doped region 1903 b. In some embodiments, the depth d₆ of the second buffer region 1962 is less than a depth d₁ of the second doped region 1903 a.

FIG. 19C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1900 c in FIG. 19C is similar to the photo-detecting apparatus 1900 a in FIG. 19A, where the difference is described below.

In some embodiments, the first switch further includes a first dielectric layer 1933 a between the absorption layer 1902 and the control contact layer 1906 a. The second switch may further include a second dielectric layer 1933 b between the absorption layer 1902 and the control contact layer 1906 b. The first dielectric layer 1933 a and the second dielectric layer 1933 a are similar to the first dielectric layer and the second dielectric layer as mentioned before, such as such as the first dielectric layer 1633 a and the second dielectric layer 1633 b as described in FIG. 16C.

FIG. 19D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 1900 d in FIG. 19D is similar to the photo-detecting apparatus 1900 c in FIG. 19C, where the difference is described below. In some embodiments, the first switch further includes a second doped region 1903 a under the control contact layers 1906 a. The second switch further includes a second doped region 1903 b under the control contact layers 1906 b. The second doped regions 1903 b, 1903 a are similar to the second doped regions as mentioned before, such as the second doped regions 1603 a, 1603 b as described in FIG. 16B.

FIG. 20A illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 a includes a substrate 2004. The photo-detecting apparatus 2000 a further includes a pixel including an absorption layer 2002 supported by the substrate 2004. The pixel includes an absorbed region AR in the absorption layer 2002. The absorbed region AR is similar to the absorbed region AR mentioned before, such as the absorbed region AR as described in FIG. 15A. The pixel further includes a carrier collection layer 2050 over the absorption layer 2002. In some embodiments, the carrier collection layer 2050 is over a first surface 2002 s of the absorption layer 2002. In some embodiments, the carrier collection layer 2050 is epitaxially formed on the first surface 2002 s of the absorption layer 2002.

The pixel further includes a first switch (not labeled) and a second switch (not labeled) electrically coupled to the absorption layer 2002. The first switch includes a control contact layer 2006 a and a readout contact layer 2008 a. The second switch includes a control contact layer 2006 b and a readout contact layer 2008 b. In some embodiments, the readout contact layers 2008 a, 2008 b and the control contact layers 2006 a, 2006 b are formed over the first surface 2050 s of the carrier collection layer 2050. In some embodiments, a width of the absorbed region AR is less than a distance between the readout contact layers 2008 a, 2008 b. In some embodiments, the readout contact layers 2008 a, 2008 b are disposed at two opposite sides of the absorbed region AR. In some embodiments, the pixel further includes a first readout circuit (not shown) and a second readout circuit (not shown) electrically coupled to the first switch and the second switch respectively for processing the collected charges. The first readout circuit is electrically coupled to the readout contact layer 2008 a. The second readout circuit is electrically coupled to the readout contact layer 2008 b. The photo-detecting apparatus 2000 a includes multiple repeating pixels. The photo-detecting apparatus 2000 a includes a pixel-array including multiple repeating pixels. In some embodiments, the pixel-array may be a one-dimensional or a two-dimensional array of pixels.

In some embodiments, a material of the carrier collection layer 2050 is different from a material of the absorption layer 2002. In some embodiments, the material of the carrier collection layer 2050 includes a semiconductor material. In some embodiments, the material of the absorption layer 2002 includes a semiconductor material. In some embodiments, the material of the absorption layer 2002 has a first band gap, and the material of the carrier collection layer 2050 has a second band gap greater than the first band gap. In some embodiments, the semiconductor material includes a group III-V semiconductor material or a group IV semiconductor material. In some embodiments, the carrier collection layer 2050 includes Si, and the absorption layer 2002 includes Ge. In some embodiments, the carrier collection layer 2050 includes amorphous Si, polycrystalline Si, crystalline Si, or a combination thereof.

In some embodiments, the carrier collection layer 2050 has a thickness less than a thickness of the absorption layer 2002. In some embodiments, the carrier collection layer 2050 has a thickness not less than 100 nm, and not more than 500 nm. In some embodiments, the thickness of the carrier collection layer 2050 is between 200 nm and 500 nm.

In some embodiments, the first switch includes a first doped region 2001 a under the readout contact layer 2008 a and in the carrier collection layer 2050. The second switch includes a first doped region 2001 b under the readout contact layers 2008 b and in the carrier collection layer 2050. In some embodiments, the first doped regions 2001 a, 2001 b are each of a first conductivity type. In some embodiments, the first doped regions 2001 a, 2001 b include a first dopant. The peak dopant concentrations of the first doped regions 2001 a, 2001 b depend on the material of the readout contact layers 2008 a, 2008 b and the material of the carrier collection layer 2050, for example, between 5×10¹⁸ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, the peak dopant concentrations of the first doped regions 2001 a, 2001 b lie in the carrier collection layer 2050. The first doped regions 2001 a, 2001 b are for collecting the carriers in the carrier collection layer 2050, wherein the carriers are generated and flow from the absorption layer 2002, which are further processed by the first readout circuit (not shown) and the second readout circuit (not shown) respectively based on the control of the two control signals cs1, cs2. In some embodiments, each of the first doped regions 2001 a, 2001 b has a depth d2. The depth d2 of each of the first doped regions 2001 a, 2001 b is less than a thickness of the carrier collection layer 2050. The depth d2 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile reaches a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, the parts of the interface between the carrier collection layer 2050 and the absorption layer 2002 and under first doped regions 2001 a, 2001 b are of or lower than a background concentration, such as 1×10¹⁵ cm⁻³.

In some embodiments, the first switch further includes a second doped region 2003 a under the control contact layers 2006 a. The second switch further includes a second doped region 2003 b under the control contact layers 2006 b. The second doped regions 2003 a, 2003 b are in the carrier collection layer 2050 and in the absorption layer 2002. In some embodiments, the second doped regions 2003 a, 2003 b cover a part of the interface between the carrier collection layer 2050 and the absorption layer 2002. In some embodiments, the second doped regions 2003 a, 2003 b are each of a second conductivity type different from the conductivity type of the first doped regions 2001 b, 2001 a. In some embodiments, each of the second doped regions 2003 a, 2003 b includes a second dopant. The peak dopant concentrations of the second doped regions 2003 a, 2003 b depend on the material of the control contact layers 2006 b, 2006 a and the material of the carrier collection layer 2050, for example, between 1×10¹⁷ cm⁻³ to 5×10²⁰ cm⁻³. In some embodiments, the peak dopant concentrations of the second doped regions 2001 a, 2001 b lie in the carrier collection layer 2050. The second doped regions 2003 a, 2003 b forms a Schottky or an Ohmic contact or a combination thereof with the control contact layers 2006 b, 2006 a. In some embodiments, each of the second doped regions 2003 a, 2003 b has a depth d1. The depth d1 of each of the second doped regions 2003 a, 2003 b is greater than the thickness of the carrier collection layer 2050. The depth d1 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of each of the second doped regions 2003 a, 2003 b reaches a background concentration, such as 1×10¹⁵ cm⁻³. In some embodiments, a dopant concentration of the second doped regions 2003 a,2003 b at the interface between the carrier collection layer 2050 and the absorption layer 102 and covered by the second doped regions 2003 a,2003 b is not less than 1×10¹⁵ cm⁻³, in some embodiments, is not less than 1×10¹⁷ cm⁻³. The second doped regions 2003 a, 2003 b are for demodulating the carriers generated in the absorption layer 2002 based on the control of the control signals cs1, cs2.

In some embodiments, the absorption function and the carrier demodulation function operate in absorption layer 202 whereas the collection of the carriers operate in the carrier collection layer 2050,

In some embodiments, since the dopant concentration of the second dopant at the interface between the carrier collection layer 2050 and the absorption layer 2002 and covered by the second doped regions 2003 a,2003 b is not less than 1×10¹⁶ cm⁻³, the dark current resulted from interface can be suppressed. Besides, a transverse field between the second doped regions 2003 a, 2003 b can be stronger at the same time. As a result, the demodulation contrast of the photo-detecting apparatus 2000 a can be improved and the dark current of the photo-detecting apparatus 2000 a can be reduced at the same time.

FIG. 20B illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 b in FIG. 20B is similar to the photo-detecting apparatus 2000 a in FIG. 20A, the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 2033 a between the second doped region 2003 a and the control contact layer 2006 a. The second switch may further include a second dielectric layer 2033 b between the second doped region 2003 b and the control contact layer 2006 b.

The first dielectric layer 2033 a prevents direct current conduction from the control contact layer 2006 a to the carrier collection layer 2050, but allows an electric field to be established within the carrier collection layer 2050 and the absorption layer 2002 in response to an application of a voltage to the control contact layer 2006 a. The second dielectric layer 2033 b prevents direct current conduction from the control contact layer 2006 b to the absorption layer 2002 but allows an electric field to be established within the carrier collection layer 2050 and the absorption layer 2002 in response to an application of a voltage to the control contact layer 2006 b. The established electric field may attract or repel charge carriers within the absorption layer 2002.

FIG. 20C illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 c in FIG. 20C is similar to the photo-detecting apparatus 2000 a in FIG. 20A, where the difference is described below. In some embodiments, the photo-detecting apparatus 2000 c further includes a blocking layer 2019 surrounding the absorption layer 2002. The blocking layer 2019 is similar to the blocking layer as described before, such as the blocking layer 1519 in FIG. 15A and FIG. 15C. The photo-detecting apparatus 2000 c further includes a conductive layer 2009 electrically coupled to the blocking layer 2019. In some embodiments, the blocking layer 2019 may be biased by a bias voltage through the conductive layer 1609 to discharge the carriers not collected by the first doped regions 2001 a, 2001 b.

FIG. 20D illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 d in FIG. 20D is similar to the photo-detecting apparatus 2000 c in FIG. 20C, where the difference is described below. In some embodiments, the first switch further includes a first dielectric layer 2033 a between the second doped region 2003 a and the control contact layer 2006 a. The second switch may further include a second dielectric layer 2033 b between the second doped region 2003 b and the control contact layer 2006 b. The first dielectric layer 2033 a and the second dielectric layer 2033 b are similar to the first dielectric layer and the second dielectric layer as described before, such as the first dielectric layer 2033 a and the second dielectric layer 2033 b in FIG. 20B.

FIG. 20E illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 e in FIG. 20E is similar to the photo-detecting apparatus 2000 c in FIG. 20C, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 2000 e further includes a channel region 2030 in the absorption layer 2002. The channel region 2030 is similar to the channel region as mentioned before, such as the channel region 1630 as described in FIG. 16A. Since the channel region 2030 and the blocking layer 2019 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between channel region 2030 and the blocking layer 2019, which may assist in separating the electron-hole pairs generated by the absorbed photons in the absorption layer 2002, for example, when the channel region 2030 is of n-type and the blocking layer 2019 is of p-type, the electrons tend to move toward the channel region 2030 and the holes tends to move toward the blocking layer 1819. The channel region 2030 is operated to collect the electrons and the blocking layer 2019 is operated to collect the holes. The channel region 2030 serves as a preliminary collector. The electrons stored in the channel region 2030 may then move to the first doped region 2001 b or the first doped region 2001 a based on the control signals cs1, cs2.

FIG. 20F illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 f in FIG. 20F is similar to the photo-detecting apparatus 2000 c in FIG. 20C, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 2000 f further includes a third doped region 2017. The third doped region 2017 is similar to the third doped region as mentioned before, such as the third doped region 1917 in FIG. 19B. In some embodiments, the third doped region 1917 has a depth d8 greater than the thickness of the carrier collection layer 2050. The depth d8 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of the third doped region 1917 reaches a background concentration, such as 1×10¹⁵ cm⁻³.

Since the third doped region 2017 and the blocking layer 2019 are collectively formed as a vertical photodiode, there is a built-in vertical electrical field established between third doped region 2017 and the blocking layer 2019, which may assist in separating the electron-hole pairs generated by the absorbed photons, for example, when the third doped region 2017 is of n-type and the blocking layer 2019 is of p-type, the electrons tends to move toward the third doped region 2017 and the holes tends to move toward the blocking layer 2019. The third doped region 2017 is operated to collect the electrons and the blocking layer 2019 is operated to collect the holes. The third doped region 2017 serves as a preliminary collector. The electrons stored in the blocking layer 2019 may be moved to first doped region 2001 a or the first doped region 2001 b based on the control signals cs1, cs2. Therefore, the quantum efficiency of the photo-detecting apparatus 2000 f is higher and the amount of the carriers moving toward the first doped region 2001 a or the first doped region 2001 b is also higher.

FIG. 20G illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 g in FIG. 20G is similar to the photo-detecting apparatus 2000 f in FIG. 20F, where the difference is described below. In some embodiments, the carrier collection layer 2050 of the pixel of the photo-detecting apparatus 2000 g further includes a hinder region 2040. The hinder region 2040 is similar to the hinder region as described before, such as the hinder region 640 as described in FIG. 6L. In some embodiments, the hinder region 2040 has a depth d9 not more than the thickness of the carrier collection layer 2050. The depth d9 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of the hinder region 2040 reaches a background concentration, such as 1×10¹⁵ cm⁻³.

The hinder region 2040 can block the carriers to be collected from reaching the first surface 2050 s of the carrier collection layer 2050, and also confine the carriers in a restricted flow path. As a result, a surface leakage current between the two second doped regions 2003 a, 2003 b of the photo-detecting apparatus 2000 g is reduced.

FIG. 20H illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 h in FIG. 20H is similar to the photo-detecting apparatus 2000 c in FIG. 20C, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 2000 h further includes counter-doped regions 2051 a, 2051 b in the carrier collection layer 2050 and the absorption layer 2002. The counter-doped regions 2051 a, 2051 b are similar to the counter-doped regions as mentioned before, such as the counter-doped region 1551 a, 1551 b as described in FIG. 15D. In some embodiments, the peak dopant concentrations of the counter-doped region 2051 a, 2051 b lie in the carrier collection layer 2050. The counter-doped regions 2051 a, 2051 b cover a part of the interface between the carrier collection layer 2050 and the absorption layer 2002. In some embodiments, each of the counter-doped regions 2051 a, 2051 b has a depth d7. The depth d7 of each of the counter-doped region 2051 a, 2051 b is greater than the thickness of the carrier collection layer 2050. The depth d7 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of the counter-doped region 2051 a, 2051 b reaches a background concentration, such as 1×10¹⁵ cm⁻³. As mentioned before, in some embodiments, the counter-doped region 2051 a, 2051 b overlaps with at least a portion of the first doped regions 2001 a, 2001 b to further reduce the dark current of the photo-detecting apparatus 2000 h.

FIG. 20l illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 i in FIG. 20l is similar to the photo-detecting apparatus 2000 e in FIG. 20E, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 20001 further includes counter-doped regions 2051 a, 2051 b in the carrier collection layer 2050 and the absorption layer 2002. The counter-doped regions 2051 a, 2051 b are similar to the counter-doped regions as mentioned before, such as the counter-doped region 2051 a, 2051 b as described in FIG. 20H. The photo-detecting apparatus 2000 i is with a lower dark current.

FIG. 20J illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 j in FIG. 20J is similar to the photo-detecting apparatus 2000 g in FIG. 20G, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 2000 j further includes counter-doped regions 2051 a, 2051 b in the carrier collection layer 2050 and the absorption layer 2002. The counter-doped regions 2051 a, 2051 b are similar to the counter-doped regions as mentioned before, such as the counter-doped region 2051 a, 2051 b as described in FIG. 20H. The photo-detecting apparatus 2000 j is with a lower dark current.

In some embodiments, the carrier collection layer 2050 of the pixel further includes a hinder region (now shown) in the carrier collection layer 2050. The hinder region is similar to the hinder region as described before, such as the hinder region 2040 as described in FIG. 20G to confine the carriers in a restricted flow path.

FIG. 20k illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 k in FIG. 20K is similar to the photo-detecting apparatus 2000 c in FIG. 20C, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 2000 k further includes a first buffer region 2061 and a second buffer region 2062. The first buffer region 2061 and the second buffer region 2062 are similar to the first buffer region 1661 and the second buffer region 1662 as described in FIG. 16F, where the difference is described below. In some embodiments, the first buffer region 2061 covers a part of the interface between the carrier collection layer 2050 and the absorption layer 2002. In some embodiments, the second buffer region 2062 covers a part of the interface between the carrier collection layer 2050 and the absorption layer 2002. In some embodiments, the dopant concentration of the fifth dopant at the interface between the carrier collection layer 2050 and the absorption layer 2002 and covered by the first buffer region 2061 and the second buffer region 2062 is not less than 1×10¹⁶ cm⁻³.

In some embodiments, the depth d5 of the first buffer region 2061 is greater than the thickness of the carrier collection layer 2050. The depth d6 of the second buffer region 2062 is greater than the thickness of the carrier collection layer 2050. The depth d5 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of the first buffer region 2061 reaches a background concentration, such as 1×10¹⁵ cm⁻³. The depth d6 is measured from the first surface 2050 s of the carrier collection layer 2050 to the position where the dopant profile of the second buffer region 2062 reaches a background concentration, such as 1×10¹⁵ cm⁻³. The first buffer region 2061 and the second buffer region 2062 can further modify the depletion regions in the carrier collection layer 2050, such as the depletion regions around the first doped regions 1601 a, 1601 b and the depletion regions near the first surface 2050 s of the carrier collection layer 2050. As mentioned before, the conductivity types of the first buffer region 2061 and the second buffer region 2062 can be the same or different from the first conductivity type of the first doped regions 2001 a, 2001 b. If the conductivity types of the first buffer region 2061 and the second buffer region 2062 are the same as the first conductivity type of the first doped regions 2001 a, 2001 b, since the dopant concentration of the fifth dopant at the interface between the carrier collection layer 2050 and the absorption layer 2002 and covered by the first buffer region 2061 and the second buffer region 2062 is not less than 1×10¹⁵ cm⁻³, which can lower the barrier at the interface for the carriers. As a result, the first buffer region 2061 and the second buffer region 2062 can facilitate the carriers flowing from the absorption layer 2002 toward the first doped regions 2001 a, 2001 b.

If the conductivity types of the first buffer region 2061 and the second buffer region 2062 are different from the first conductivity type of the first doped regions 2001 a, 2001 b, the flow of the carries can be confined at a path away from the first buffer region 2061 and the second buffer region 2062, and thus. As a result, the demodulation contrast of the photo-detecting apparatus 2000 k can be improved.

In some embodiments, the pixel of the photo-detecting apparatus 2000 k may further includes counter-doped regions 2051 a, 2051 b in the carrier collection layer 2050 and the absorption layer 2002. The counter-doped regions 2051 a, 2051 b are similar to the counter-doped regions as mentioned before, such as the counter-doped region 2051 a, 2051 b as described in FIG. 20H to further lower the dark of the photo-detecting apparatus 2000 k.

FIG. 20L illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 20001 in FIG. 20L is similar to the photo-detecting apparatus 2000 k in FIG. 20K, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 20001 further includes a channel region 2030 in the absorption layer 2002. The channel region 2030 is similar to the channel region as mentioned before, such as the channel region 2030 as described in FIG. 20E to further improve the demodulation contrast of the photo-detecting apparatus 2000L.

FIG. 20M illustrates a cross-sectional view of a photo-detecting apparatus, according to some embodiments. The photo-detecting apparatus 2000 m in FIG. 20M is similar to the photo-detecting apparatus 2000 k in FIG. 20K, where the difference is described below. In some embodiments, the pixel of the photo-detecting apparatus 20001 further includes a third doped region 2017. The third doped region 2017 is similar to the third doped region as mentioned before, such as the third doped region 2017 as described in FIG. 20G to further improve the demodulation contrast of the photo-detecting apparatus 2000 m.

In some embodiments, the carrier collection layer 2050 of the pixel of the photo-detecting apparatus 2000 m further includes a hinder region (now shown). The hinder region is similar to the hinder region as described before, such as the hinder region 2040 as described in FIG. 20G to confine the carriers in a restricted flow path.

In some embodiment, the photo-detecting apparatus in FIG. 20A-20M may further include two first silicide regions under the readout contact layers 2008 a, 2008 b. The first silicide regions are in the carrier collection layer 2050 and may be similar to the first silicide regions 513 a′, 513 b′ as described in FIG. 5B. In some embodiment, the photo-detecting apparatus in FIGS. 20A, 20C, and 20E-20M may further include two second silicide regions under the control contact layer 2006 a, 2006 b. The second silicide regions are in the carrier collection layer 2050 and may be similar to the second silicide regions 515 a′, 515 b′ as described in FIG. 5B.

In some embodiments, the first switch of the photo-detecting apparatus 2000 e to 2000 m may further include a first dielectric layer between the second doped region 2003 a and the control contact layer 2006 a. The second switch of the photo-detecting apparatus 2000 e to 2000 m may further include a second dielectric layer between the second doped region 2003 b and the control contact layer 2006 b. The first dielectric layer and the second dielectric layer are similar to the first dielectric layer and the second dielectric layer as described before, such as the first dielectric layer 2033 a and the second dielectric layer 2033 b in FIG. 20B.

In some embodiments, the photo-detecting apparatus in FIG. 1A-1J, in FIGS. 2A-2H, in FIGS. 3A-3B, in FIG. 4A-4H, in FIG. 5A-5H, in FIG. 6A-6C, in FIG. 6H-6V, FIG. 7A-7D, in FIG. 8A-8B, in FIG. 15A-15D, in FIG. 16A-16M, in FIG. 17A-17I, in FIG. 18A-18U, in FIGS. 19A-19D and in FIG. 20A-20M further include an isolation region as described before, such as the isolation region 624 in FIG. 6D or the isolation region 1524 in FIG. 15E.

In some embodiments, the photo-detecting apparatus in FIG. 1A-1H, in FIGS. 2A-2H, in FIGS. 3A-3B, in FIG. 4A-4H, in FIG. 6A-6H, in FIG. 6K-6M, FIG. 6O, FIG. 6Q-FIG. 6V, FIG. 9A-9E, FIG. 15A-15L, FIG. 16A-16B, FIG. 16E-16K, FIG. 19A-19B further include a passivation layer 514 as described in one of the FIGS. 5A-5H as long as the person having ordinary skill in the technical field can produce.

In some embodiments, the photo-detecting apparatus in the present disclosure further includes an optical element (not shown) over the pixel. In some embodiments, the photo-detecting apparatus in the present disclosure further includes multiple optical elements (not shown) over the multiple pixels. The optical element converges an incoming optical signal to enter the absorbed region. In some embodiments, the optical elements include lenses.

In some embodiments, p-type dopant includes a group-III element. In some embodiments, p-type dopant is boron. In some embodiments, n-type dopant includes a group-V element. In some embodiments, n-type dopant is phosphorous

In the present disclosure, if not specifically mention, the absorption layer is entirely embedded in the substrate, partially embedded in the substrate or entirely on the first surface of the substrate. Similarly, if not specifically mention, the germanium-based light absorption material is entirely embedded in the semiconductor substrate, partially embedded in the semiconductor substrate or entirely over the first surface of the semiconductor substrate.

In the present disclosure, if not specifically mention, the absorption layer is configured to absorb photons having a peak wavelength in an invisible wavelength range not less than 800 nm, such as 850 nm, 940 nm, 1050 nm, 1064 nm, 1310 nm, 1350 nm, or 1550 nm. In some embodiments, the invisible wavelength range is not more than 2000 nm. In some embodiments, the absorption layer receives an optical signal and converts the optical signal into electrical signals.

In the present disclosure, if not specifically mention, the substrate is made by a first material or a first material-composite. The absorption layer is made by a second material or a second material-composite. The second material or a second material-composite is different from the first material or a first material-composite. In some embodiments, the absorption layer includes a semiconductor material. In some embodiments, the absorption layer includes polycrystalline material. In some embodiments, the substrate includes a semiconductor material. In some embodiments, the absorption layer includes a Group III-V semiconductor material. In some embodiments, the substrate includes a Group III-V semiconductor material. The Group III-V semiconductor material may include, but is not limited to, GaAs/AlAs, InP/InGaAs, GaSb/InAs, or InSb. In some embodiments, the absorption layer includes a semiconductor material including a Group IV element. For example, Ge, Si or Sn. In some embodiments, the absorption layer includes Ge_(x)Si_(1-x), wherein 0<x<1. In some embodiments, the absorption layer includes the Si_(x)Ge_(y)Sn_(1-x-y), wherein 0 x 1, 0 y 1. In some embodiments, the absorption layer includes the Ge_(1-a)Sn_(a), wherein 0 a 0.1. In some embodiments, the substrate includes Si. In some embodiments, the substrate is composed of Si. In some embodiments, the absorption layer is composed of Ge, Si or Ge_(x)Si_(1-x). In some embodiments, the absorption layer composed of intrinsic germanium is of p-type due to material defects formed during formation of the absorption layer, wherein the defect density is from 1×10¹⁴ cm⁻³ to 1×10¹⁶ cm⁻³.

In the present disclosure, if not specifically mention, the absorption layer has a thickness depending on the wavelength of photons to be detected and the material of the absorption layer. In some embodiments, when the absorption layer includes germanium and is designed to absorb photons having a wavelength not less than 800 nm, the absorption layer has a thickness not less than 0.1 um. In some embodiments, the absorption layer includes germanium and is designed to absorb photons having a wavelength between 800 nm and 2000 nm, the absorption layer has a thickness between 0.1 um and 2.5 um. In some embodiments, the absorption layer has a thickness between 1 um and 2.5 um for higher quantum efficiency. In some embodiments, the absorption layer may be grown using a blanket epitaxy, a selective epitaxy, or other applicable techniques.

In the present disclosure, if not specifically mention, the first readout circuits, the second readout circuits, may be in a three-transistor configuration consisting of a reset gate, a source-follower, and a selection gate, a circuit including four or more transistors, or any suitable circuitry for processing charges. In some embodiments, the first readout circuits and the second readout circuits may be fabricated on the substrate. In some other embodiments, the first readout circuits and the second readout circuits may be fabricated on another substrate and integrated/co-packaged with the absorption layer via die/wafer bonding or stacking.

In the present disclosure, if not specifically mention, the first readout circuit includes a first capacitor. The first capacitor is configured to store the photo-carriers collected by one of the first doped regions. In some embodiments, the first capacitor is electrically coupled to the reset gate of the first readout circuit. In some embodiments, the first capacitor is between the source-follower of the first readout circuit and the reset gate of the first readout circuit. In some embodiments, the second readout circuit includes a second capacitor. In some embodiments, the second capacitor is configured to store the photo-carriers collected by the other one of the first doped regions. In some embodiments, the second capacitor is electrically coupled to the reset gate of the second readout circuit. In some embodiments, the second capacitor is between the source-follower of the second readout circuit and the reset gate of the second readout circuit. Examples of the first capacitor and the second capacitor include, but not limited to, floating-diffusion capacitors, metal-oxide-metal (MOM) capacitors, metal-insulator-metal (MIM) capacitors, and metal-oxide-semiconductor (MOS) capacitors.

In the present disclosure, if not specifically mention, the light shield has the optical window for defining the position of the absorbed region in the absorption layer. In other words, the optical window is for allowing the incident optical signal enter into the absorption layer and defining the absorbed region. In some embodiments, the light shield is on a second surface of the substrate distant from the absorption layer when an incident light enters the absorption layer from the second surface of the substrate. In some embodiments, a shape of the optical window can be ellipse, circle, rectangular, square, rhombus, octagon or any other suitable shape from a top view of the optical window.

In the present disclosure, if not specifically mention, the collection of the charges by the two switches of a pixel may be altered over time, such that the photo-detecting apparatus applied to an imaging system may determine phase information of the sensed light. The imaging system may use the phase information to analyze characteristics associated with the three-dimensional object including depth information or a material composition. The imaging system may also use the phase information to analyze characteristics associated with facial recognition, eye-tracking, gesture recognition, 3-dimensional model scanning/video recording, motion tracking, and/or augmented/virtual reality applications. In some embodiments, the photo-detecting apparatus is configured for time-of-flight detection. The imaging system may be a mobile device (e.g., a smartphone or a tablet), an ancillary device (e.g., a wearable device) for a mobile device, a computing system on a vehicle or in a fixed facility (e.g., a factory), a robotics system, or any other suitable device and/or system. In some embodiments, an imaging system may include one or more optical modules. For example, an optical module may include one or more cameras that are integrated with the photo-detecting apparatus. As another example, one optical module of an imaging system may include one or more cameras, and another optical module of the imaging system may include a photo-detecting apparatus having a one-dimensional or a two-dimensional array of pixels implemented for time-of-flight detection for obtaining time-of-flight information.

In the present disclosure, in some embodiments, one of the control signals may be fixed at a voltage value Vi, and the other control signal may alternate between voltage values Vi±ΔV. In some embodiments, the two control signals may be voltages that are differential to each other. In some embodiments, one of the control signals is a constant voltage signal (e.g., 0.5 v) and the other control signal is a time-varying voltage signal (e.g., sinusoid signal, clock signal or pulse signal operated between 0V and 1V). The direction of the bias value determines the drift direction of the charges generated from the absorption layer.

In the present disclosure, if not specifically mention, in a same pixel, the type of the carriers collected by the first doped region of one of the switches and the type of the carriers collected by the first doped region of the other switch are the same. For example, when the photo-detecting apparatus is configured to collects electrons, when the first switch is switched on and the second switch is switched off, the first doped region in the first switch collects electrons of the photo-carriers generated from the absorption layer, and when the second switch is switched on and the first switch is switched off, the first doped region in the second switch also collects electrons of the photo-carriers generated from the absorption layer.

In some embodiments, each of the switches further includes a portion of the absorption layer and/or a portion of the substrate or a portion of the carrier control layer or a portion of the carrier collection layer. In some embodiments, the readout contact layer of each of the switches is electrically coupled to and arranged over the respective portion of absorption layer and/or the substrate or the carrier control layer or the carrier collection layer. In some embodiments, each portion of the absorption layer and/or the substrate or the carrier control layer or the carrier collection layer of the two switches further includes a first doped region arranged under the respective readout contact layer.

In some embodiments, each of the switches includes another portion of the absorption layer and/or another portion of the substrate or another portion of the carrier control layer or another portion of the carrier collection layer. In some embodiments, the control contact layer of each of the switches is electrically coupled to and arranged over the respective portion of absorption layer and/or the substrate or the carrier control layer or the carrier collection layer. In some embodiments, each portion of the absorption layer and/or the substrate or carrier control layer or the carrier collection layer of the two switches further includes a second doped region arranged under the respective control contact layer.

In some embodiments, the first dielectric layer, the second dielectric layer, the third dielectric layer, the fourth dielectric layer and the fifth dielectric layer in the present disclosure include, but is not limited to SiO₂. In some embodiments, the first dielectric layer, the second dielectric layer the third dielectric layer, the fourth dielectric layer and the fifth dielectric layer include a high-k material including, but is not limited to, Si₃N₄, SiON, SiN_(x), SiO_(x), GeO_(x), Al₂O₃, Y₂O₃, TiO₂, HfO₂ or ZrO₂. In some embodiments, the first dielectric layer, the second dielectric layer, the third dielectric layer, the fourth dielectric layer and the fifth dielectric layer in the present disclosure include semiconductor material but, but is not limited to amorphous Si, polycrystalline Si, crystalline Si, or a combination thereof.

In the present disclosure, if not specifically mention, the readout metal line, control metal line, readout contact layer, the control contact layer and the conductive layer include metals or alloys. For example, the readout metal line, control metal line, readout contact layer, the control contact layer and the conductive layer include Al, Cu, W, Ti, Ta—TaN—Cu stack or Ti—TiN—W stack.

In the present disclosure, if not specifically mention, the third doped region and the blocking layer in the photo-detecting apparatus according to the present disclosure can be floating, open, short or biased by a voltage source or a current source such as bias voltage ca1 or ca2.

In some embodiments, if not specifically mention, the pixel-array can be arranged in a way similar, but not limited to the pixel array in FIG. 12A and FIG. 12B.

In some embodiments, if not specifically mention, the cross-sectional views shown in the present disclosure may be a cross-sectional view along any possible cross-sectional line of a photo-detecting apparatus.

As used herein and not otherwise defined, the terms “substantially” and “about” are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can encompass instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can encompass a range of variation of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

While the invention has been described by way of example and in terms of a preferred embodiment, it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims. 

What is claimed is:
 1. A photo-detecting apparatus, comprising: a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer comprising: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×10¹⁵ cm⁻³, wherein a distance between the first surface and a location of the channel region having the peak dopant concentration is less than a distance between the second surface and the location of the channel region having the peak dopant concentration, and wherein the distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm.
 2. The photo-detecting apparatus of claim 1 further comprising: two switches, each switch comprising a first portion of the absorption layer and a control contact layer that is electrically coupled to and arranged over a respective first portion of absorption layer.
 3. The photo-detecting apparatus of claim 2, wherein the channel region is arranged between the two switches and the second surface along a direction substantially perpendicular to the first surface of the absorption layer.
 4. The photo-detecting apparatus of claim 2, wherein each switch comprises a second portion of the absorption layer and a readout contact layer electrically coupled to and arranged over a respective second portion of absorption layer, wherein each second portion of the absorption layer of the two switches further comprises a first doped region of a first conductivity type, and wherein each of the first doped regions is electrically coupled to a respective readout contact layer.
 5. The photo-detecting apparatus of claim 4, wherein a conductivity type of the channel region is a same conductivity type as the first conductivity type of the first doped regions.
 6. The photo-detecting apparatus of claim 4, wherein the absorption layer further comprises a hinder region that is arranged between two first doped regions and arranged between the channel region and the first surface.
 7. The photo-detecting apparatus of claim 6, wherein the hinder region has a dopant profile having a peak dopant concentration different from the peak dopant concentration of the channel region.
 8. The photo-detecting apparatus of claim 6, wherein a conductivity type of the hinder region is the same as the conductivity type of the channel region, and the peak dopant concentration of the hinder region is lower than the peak dopant concentration of the channel region.
 9. The photo-detecting apparatus of claim 6, wherein a conductivity type of the hinder region the hinder region is different from the conductivity type of the channel region, and the peak dopant concentration of the hinder region is higher than the peak dopant concentration of the channel region.
 10. The photo-detecting apparatus of claim 9, wherein the peak dopant concentration of the hinder region is between 1×10¹⁸ cm⁻³ and 5×10²⁰ cm⁻³.
 11. The photo-detecting apparatus of claim 4, wherein the channel region is overlapped with the first doped regions.
 12. The photo-detecting apparatus of claim 4, wherein each second portion of the absorption layer of the two switches further comprises a second doped region arranged between a respective control contact layer and the second surface of the absorption layer, wherein each of the second doped regions is of a second conductivity type different from the first conductivity type.
 13. The photo-detecting apparatus of claim 4, further comprising two counter-doped regions, wherein each of the two counter-doped regions overlaps with at least a portion of the first doped regions, and the two counter-doped regions are of a conductivity type different from the first conductivity type of the first doped regions.
 14. The photo-detecting apparatus of claim 4, further comprising a first buffer region and a second buffer region between two first doped regions.
 15. The photo-detecting apparatus of claim 14, wherein each of the first buffer region and the second buffer region includes a depth less than a depth of each of the first doped regions.
 16. The photo-detecting apparatus of claim 2, wherein a width of the channel region is greater than a distance between control contact layers.
 17. The photo-detecting apparatus of claim 1, wherein a width of the channel region is between 10 nm and 500 nm.
 18. The photo-detecting apparatus of claim 1, wherein the distance between the first surface of the absorption layer and the location of the peak dopant concentration of the channel region is between 50 nm and 650 nm.
 19. The photo-detecting apparatus of claim 1, wherein the peak dopant concentration of the channel region is between 1×10¹⁵ cm⁻³ and 5×10¹⁷ cm⁻³.
 20. An imaging system comprising: one or more cameras; and a photo-detecting apparatus comprising a pixel-array for time-of-flight information, each pixel of the pixel-array comprising: a substrate made by a first material or a first material-composite; an absorption layer made by a second material or a second material-composite, the absorption layer being supported by the substrate and the absorption layer comprising: a first surface; a second surface arranged between the first surface and the substrate; and a channel region having a dopant profile with a peak dopant concentration equal to or more than 1×10¹⁵ cm⁻³, wherein a distance between the first surface and a location of the channel region having the peak dopant concentration is less than a distance between the second surface and the location of the channel region having the peak dopant concentration, and wherein the distance between the first surface and the location of the channel region having the peak dopant concentration is not less than 30 nm. 